Eidolon Teralyst

"Rising from the lakes at sundown and returning to them before dawn these simple-minded monstrosities roam the nighttime plains, howling, searching for a thing they can barely remember: completeness. Wholeness. An intelligence and malevolent purpose which, fate willing, they will never return to again."

- Fragment description

Teralysts are gigantic spectral Sentient creatures found on the Plains of Eidolon at night. They are remnants of a Sentient that was defeated in a battle against the Tenno during the Old War, whose remains now wander the plains perpetually searching for their lost components. These fragments are, however, still formidable creatures armed with powerful attacks and near-impenetrable defenses, and are hostile to both Tenno and Grineer alike.

Behavior
Teralysts emerge from bodies of water on the Plains at the fall of night accompanied by a column of blue light marking their location. They generally walk in one direction, even if the Tenno are nearby, though their attention can be drawn to specific locations by using Eidolon Lures found throughout the Plains at night.

The Teralyst has many different attacks and several do extremely high damage, but they are all telegraphed. Once acquainted, it is possible to easily avoid the most damaging attacks.
 * Seeking Bullets: A sphere of light emitted from the Teralyst's back which splits into multiple homing projectiles. These are not very accurate, and are easily avoided.
 * Ground Stomp: Stomps the ground, sending out a ground shockwave that knockbacks back any Tenno in its path a great distance (100 meter radius).
 * Ground Smash: Smashes the ground, sending out a series of high-damaging, homing quakes to the Tenno's position. These homing quakes can stun the Tenno and are 25m high.
 * Gun Swing: Swings its gun arm while firing it in a wide arc, each bullet creating a 2m wide explosion.
 * Tree Swing: Swings its tree arm in a short arc, dealing heavy damage.
 * Summoning Scream: The Teralyst glows orange and screeches into the air. This will summon and buff Vomvalysts around it.
 * Regenerating Scream: The Teraylst glows blue and screeches. This will cause surrounding Vomvalysts (that are not affected by Summoning Scream) to link to the Teralyst and begin to regenerate its shield. Additionally, this will render it invulnerable to all damage until all linked Vomvalysts are destroyed.
 * Sentient Residue: The Teralyst will "bleed" teal blood on the ground after losing at least one of its Synovia, dealing damage over time to those standing on it.
 * Star Fall: Fires its gun into the sky, causing a rain of explosive, slightly homing projectiles on all targets nearby. The explosives may cause knockdown. This ability can deal damage through Limbo's Rift Plane and Frost's Snow Globe. Base area-of-effect spans 200m in radius.
 * Energy Spikes: The attack Teralyst uses upon the destruction of one of his limbs. This will emit five pulses of high damaging damage. He will repeat this three times.
 * Additionally, destroyed arm Synovias will emit Seeking Bullets that have stronger homing capabilities, and leg Synovias will shoot out arcing shots of Sentient Residue that last a shorter duration.

General
Due to the Teralyst possessing both Alloy Armor and Robotic health, weapons with damage will do maximum damage (+75% vs Alloy Armor, +25% vs Robotic), whilst  will also be reasonably effective (+15% vs Alloy Armor, +25% vs Robotic). Avoid and  as much as possible. is recommended to decrease Teralyst's armor. has no effect on its shields. Note that the Teralyst is immune to all Status Effects.

Weapons with a high damage to ammo ratio are recommended. Snipers and shotguns are ideal for this purpose. Explosives are ineffective on the weak points as they will hit the invulnerable body and deal no damage.

The Teralyst is immune to all debuffing effects of Warframe powers. Therefore, highly defensive and/or self/squad buffing warframes such as Rhino's Iron Skin & Roar, Trinity's Blessing, Chroma's Cold Elemental Ward and Vex Armor, Volt's Electric Shield, or Harrow's Covenant are good choices.

Some Warframes are well-equipped to fight the Eidolon Teralyst for the utility they bring into the party:
 * Chroma can quickly shred and even one-shot the Synovia limbs by using Vex Armor's Fury buff extensively. Fury can be quickly charged by using self-damaging weapons such as the Angstrum or Hikou (with . It is recommended to equip a Decaying Dragon Key to self-damage faster, and not recommended to equip and  on their Sentinels as they actively interfere with self-damage. An alternative is to utilize  damage into their weapons to charge the Fury buff even faster.
 * Trinity's Blessing will provide extra survivability to the entire squad, as well as making sure the Eidolon Lures are topped up.
 * Harrow's Covenant can be used to render the squad immune to the proc of the energy spike the Teralyst emits, and provide a maximum damage buff based on the massive amount of damage prevented. Duration should be normalized, so as not to interfere with Chroma's Vex Armor.
 * Rhino's Roar ability can be used to increase the overall party DPS, given how durable the Teralyst is. Furthermore, due to the lack of CC required, a Rhino can opt to maximize their Power Strength to provide a whopping +186% damage buff.
 * Volt's Electric Shield, ontop of their damage and crit enhancing capability, is perhaps the only ability in the game which can enhance the Operator's damage, making them a solid choice if the Teralyst's shield are a concern.
 * Titania's Razorwing enables her to fly above virtually all of the Teralyst's attacks and allows her to deal sustained, immense amounts of damage. Stay moving to avoid fire from the Vomvalysts.
 * Octavia's Amp ability can vastly increase damage dealt by weapons for the entire squad, with enough Ability Strength; however, make sure to cast the ability where attacking the Teralyst or its Synovia is the most convenient. Metronome and its Nocturne buff also allows the squad to evade the Teralyst's seeking bullets and the Vomvalysts' attacks.
 * Oberon's Hallowed Ground can render allies standing on it immune to status, as well as provide healing with Renewal. Phoenix Renewal can provide additional support and Smite Infusion can provide additional Radiation damage which is very effective against the Teralyst.

During any phase of the battle, players can bring Eidolon Lures into the battle and charge them by either letting them absorb three Vomvalysts in their spectral ethereal form, or by picking up the energy orb they drop (indicated by a blue beacon) and passing it onto the Lure. Once they are are charged, they will glow blue and if brought near the Teralyst, they will prevent it from teleporting away.

Phase 1
The Teralyst possesses a Sentient shield which is invulnerable to all sources of damage, it can only be harmed with damage which can only be utilized by the Tenno Operator. If depleted, the Eidolon's limbs -- Teralyst Synovia -- will become vulnerable to damage. Note that their shield can still regenerate after a moderate delay of not taking any damage.

It is possible to reduce the health of all Synovia to around 15 percent before destroying one as the Teralyst cannot use its Regenerating Scream until at least one of the Synovia has been destroyed. This approach effectively eliminates the chances of Regenerating Scream taking place, and dramatically accelerates the encounter.

If one of their Synovia limbs have been destroyed, it will drop an Exceptional Sentient Core. The boss will then retaliate by emitting an Energy Spike -- which is a massive pulse expanding up to 60 meters away -- and then teleport away from the Tenno and recovering all of their shield. However, if there are at least one charged Eidolon Lure to tether them, this teleportation can be prevented and the boss will only recover half its shield.

Phase 2
Once two weak points have been destroyed, it will begin two new attack patterns while modifying the aggressiveness of the Vomvalyst adds.


 * Firstly, the Teralyst will perform Star Fall -- in which the Teralyst shoots into the sky causing a hailstorm of homing explosives, covering a huge area around the Teralyst in explosion. Staying airborne may help avoid these carpet bombs.
 * Secondly, the Teralyst will follow it up with Ground Smash -- in which the Teralyst smashes the ground sending a series of homing quakes -- spread in a starburst pattern instead of circling outwards. This pattern does not change until all weak points have been destroyed.
 * Finally, the Eidolon Vomvalysts spawned around the Teralyst will launch exploding spheres instead which deals more damage.

Once three Synovia limbs have been destroyed, the Teralyst will attack more frequently and aggressively, and Ground Stomp will be followed by a slower damaging blue ring. The Vomvalyst spawn rate will increase notably.

Phase 3
Once all four Synovia limbs have been destroyed, the Teralyst will drop down and summon a school of Eidolon Vomvalysts in their ethereal form to assimilate with it. Each Vomvalysts that assimilates with the Teralyst will heal itself. The players should intercept and kill as many as possible. This phase will last for a moderate time and will end automatically after.

Phase 4
In this phase, the Teralyst will not regenerate its shields and can be killed entirely once and for all. Their attack pattern closely resembles third phase's pattern.

Once the Teralyst dies, it will drop to the ground, droping an Eidolon Shard as well as one of the, , , or mods.

If successfully defeated while tethered by at least two charged Eidolon Lures, the Teralyst will be captured the lures will self-destruct and yield an additional four Intact Sentient Cores, two Exceptional Sentient Cores, a Flawless Sentient Core, and a Brilliant Eidolon Shard; all of which drop from the lures and not the corpse of the Teralyst. To know that the requirement of capture is fulfilled, listen for Quill Onkko's comment that "Sentient energy is contained".

Summary

 * Preparation Phase: Damage an Eidolon Lure and hack it to take control of it. The Lure can then be charged by either letting it absorb a nearby Eidolon Vomvalyst's spectral form, or by picking up the energy orb they drop (indicated by a blue beacon) and passing it onto the Lure. Each lure needs the energy of three Vomvalysts to fully charge. It is recommended to have two lures under control by the end of the hunt.
 * Phase 1: The Eidolon Teralyst's shield can only be damaged with damage; this can be done with the Operator's power. The Synovia weak points will be vulnerable once its shields have been depleted.
 * Phase 2: Take down Synovia; this will trigger an energy spike of 5 waves in a 65 meter radius and yield an Exceptional Sentient Core for each one destroyed.
 * With no charged Lure: The Teralyst will teleport away, regenerating all of its shield.
 * With at least 1 charged Lure: The Teralyst will not teleport away, regenerating only half of its shield.
 * Phase 3: Once all Synovia have been destroyed, the Teralyst will call upon surrounding Vomvalysts to heal it. Destroy these with the Operator.
 * Phase 4: The Teralyst's entire body will finally be vulnerable to damage. At this point it can be defeated.
 * With no charged Lure: The Teralyst will collapse to the ground, yielding only an Eidolon Shard.
 * With 1 charged Lure: The Teralyst will collapse to the ground as if it weren't tethered, yielding only an Eidolon Shard. The charged Lure will remain unused.
 * With at least 2 charged Lures: The Teralyst will be absorbed and dissolved into the ground, the Lures tethered to it yielding a generous amount of Sentient Cores and a Brilliant Eidolon Shard, in addition of an Eidolon Shard.

Tips

 * The Operator's Void Mode is the best way to avoid damage from all of the Teralyst's area of effect attacks, as Void Mode renders the Operator immune to all forms of damage, while leaving the Warframe similarly invulnerable to attack while the Operator is out. Companions remain vulnerable however, so using Void Dash to escape attacks and exiting Transference to teleport your warframe as well as your vulnerable companions away might be a better solution.
 * The Eidolon Lures do not take damage from the Teralyst's energy spike.
 * Remember to keep the Eidolon Vomvalyst count around the Teralyst to a minimum, as they can be a threat if ignored and enables the boss to regenerate their shields via the Vomvalysts.
 * The Shwaak Prism greatly aids against the Eidolon Sentients, with its innate Punch Through dealing multiple counts of damage to the Teralyst as well as killing groups of Eidolon Vomvalysts.
 * It is recommended that players with Eidolon Lures following them should not be the main source of damage in the squad, as the lures seem to frequently drift in front of the player, blocking shots and preventing the player from damaging the Teralyst.
 * Throughout the fight, only one charged Eidolon Lure is required to tether the Teralyst. Therefore, a second one can be charged later into the fight, if the players so chose.
 * Trinity's Blessing is invaluable for healing Eidolon Lures, especially against the Teralyst's area-of-effect attacks. Her abilities are also useful in keeping Companions alive against said attacks.
 * An Energy Vampire Trinity is not advised as Eidolon Vomvalysts in their spectral form are unaffected by Energy Vampire, which may be a problem for groups that kill Vomvalysts as fast as possible.
 * While less effective at doing so, Oberon's Renewal ability can provide a similar level of healing to better sustain Teralyst attacks. Additionally, Oberon can use his Hallowed Ground plus Renewal combo to cast the Iron Renewal armor buff on allies, making them more resistant to attacks.
 * Hallowed Ground skill will nullify the Proc effect from the pulse burst, but not the damage.
 * Amesha's abilities are very useful for the fight:
 * Benevolent Decoy can absorb the Star Fall and Seeking Bullets attack and turn them into healing pulses.
 * Warding Grace can block the Teralyst's magnetic procs.
 * Vengeful Rush can be used to render you and your allies invulnerable while they don't have a full energy pool.
 * This can be used to tank the Teralyst's magnetic blasts between stages.
 * Itzal's Cosmic Crush can be used to vacuum all the Teralyst loot in one place.
 * If the Teralyst is still alive shortly before sunrise, it will change course towards the nearest body of water. Upon arriving, it will become invulnerable and disappear in a pillar of blue light as it sinks back in. The Teralyst can still be killed en route as long as it has not reached the water, provided there is no more than a single Synovia remaining. When Onkko warns the player of the impending sunrise, all lures will inevitably self-destruct, and capture will become impossible.
 * Konzu's bounty reset timer coincides with when the Teralyst will flee.
 * can remove the Teralyst's armor, even while it's shielded; 50 hits will remove the Teralyst's armor entirely, though doing so will also remove its weakness to damage. Hitting the Teralyst 49 times instead will minimize its armor and retain its damage weakness.
 * If the Teralyst teleports away, it will emit a highly visible pillar of light wherever it arrives. Additionally, all nearby Vomvalysts will attempt to reconvene with the Teralyst, regardless of distance. A Titania in Razorwing or any player with an Archwing Launcher can easily fly up and locate the pillar.
 * Similarly, upon entering the fields, the Teralyst's initial spawn will be accompanied by the same pillar of light.

Bugs

 * After killing a Teralyst, the doors back to Cetus may not open.
 * Exceptional Cores may not drop for some players or be dropped up to 30m away.
 * The Teralyst may occasionally begin rapidly flying upwards, then abruptly fall to the ground shortly after reaching the height limit.
 * The Teralyst may randomly turn invisible during the fight. It is still possible to damage the shield/limbs with certain weapons, however the hit-box for the limbs is inconsistent and may require many 'test shots' in order to damage one successfully. If a limb is destroyed while it is in this state it will instantly teleport to a random spawn location.
 * Due to a 0.02% drop rate that is un-accounted for, the Teralyst may drop one of the slash set mods (,, or .)

Trivia

 * It was revealed on Devstream #102 that Eidolon vocal sound effects were made using humpback whales' calls.