Eidolon Teralyst

Teralysts are gigantic Sentient creatures found in the Plains of Eidolon at night. They are remnants of the Sentient that was defeated in a battle against the Tenno in an ancient war, and now wander aimlessly in the fields devoid of purpose. Despite this, the Teralysts are still formidable creatures  armed with powerful attacks and durable defenses, and are hostile to both Tenno and Grineer alike.

Behavior
Teralysts generally walk in one direction, even if Tenno are nearby, though their attention can be drawn to specific locations by using Eidolon Lures found throughout the Plains at night.

Upon one of the Teralyst's weak points being destroyed, it will emit a massive energy wave that procs after a short delay, then teleport to a random part of the map if not chained by an Eidolon Lure.

The Teralyst has many attacks, though all of them have noticeable telegraphing:


 * Ground Stomp: Stomps the ground, sending out a shock wave that pushes any warframe or operator in its path back a great distance. Jumping will dodge this ability.
 * Ground Smash: Sends a series of explosions to each Tenno's current position. Moving after the ability is cast can successfully prevent the damage.
 * Gun Swing: Teralyst takes its gun (left arm) and swings it in a wide arc. The gun may be firing during this action, creating a 2 meter wide beam.
 * Star Fall: Teralyst fires a massive amount of bullets into the air, after which they rain down on all targets nearby. Being in the air seems to avoid the damage outright. Damages through Limbo's Rift Plane, Frosts Snow Globe also does not block damage.
 * Seeking Bullets: A ball of light is emitted. After a short delay, many projectiles appear and seek out any nearby targets. This attack does not seem to be very accurate, and is easily dodged.
 * Tree Swing: Swings its right arm in a short arc, dealing damage in an area.
 * Sentient Residue: The Teralyst will leave residue behind when it walks or around on the ground randomly in later stages. This deals damage over time to players standing on it.
 * Summoning Scream: The Teralyst glows orange and screeches in the air. This will summon and buff Vomvalysts around it.
 * Regenerating Scream: The Teraylst glows blue and screeches. This will cause surrounding Vomvalysts to link to the Teralyst and begin to regenerate its shield. It is imperative to kill all of the linked Vomvalysts as fast as possible.
 * Additionally, destroyed arm weak points will spit the Seeking Bullets homing shots, and leg points will shoot out arcing shots that explode into Sentient Residue.

Strategy
Teralyst has many different attacks and several do extremely high damage, but they are all telegraphed. Once acquainted, players should be able to easily avoid the most damaging attacks.

Recommended equipment
Weapons with a high damage to ammo ratio. Snipers and shotguns are ideal for this purpose. Explosives are ineffective on the weak point phases as they will 'hit' the body and deal no damage.

Due to possessing both Alloy Armor and Robotic health, weapons equipped with damage will do maximum damage (+75% vs Alloy Armor, +25% vs Robotic), whilst  will also be reasonably effective (+25% vs Alloy Armor, +15% vs Robotic). If the entire squad is equipped with Corrosive Projection, the Teralyst will have all its Alloy Armor removed. Avoid and  as much as possible. Shield Disruption also has no effect on its shields.

The Teralyst is immune to all non-damage effects of warframe powers, as well as all status effects. 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, or Harrow's Covenant are good choices.

Titania's Razorwing enables her to fly above virtually all of the Teralyst's attacks and allows her to deal immense amounts of damage. Stay moving to avoid fire from the Vomvalysts.

Limbo's Rift Plane can dodge all but the charges of the Vomvalysts, the Star Fall attack, and the explosions upon the destruction of a weak point.

Chroma can charge their Vex Armor by using self-damaging weapons such as Angstrum or Hikou modded with Concealed Explosives.

Harrow's Covenant can be used to render the squad immune to the energy wave the Teralyst emits. Duration should be normalized, as to not interfere with Chroma's Vex Armor.

During any phase of the battles, players can bring Eidolon Lures into the battle and charge them by letting them absorb the Vomvalysts while they are incorporeal. Once the lures are charged, the lures will glow blue and if brought near the Teralyst before a part is destroyed will prevent the Teralyst from teleporting away.

Stage 1
First the shields have to be removed, as until this is done the Teralyst cannot be damaged. Using the Operator's Void Beam is the only way to remove the shields. Dashing in and out of Transference or using Void Mode can help prevent damage during this stage, allowing all members to focus on removing the shield instead of healing others.

When no shields are present, there are four weak points called Teralyst Synovia, one for each of its arms and legs, that can be targeted. It is advisable to only focus on one point at a time.

Once a weak point is destroyed, the Teralyst will drop a Exceptional Sentient Core and emit 6 damaging pulses dealing 1000 damage per pulse in a 60m radius with a guaranteed  proc. The blast comes after a delay and takes time to expand, allowing players to get out of the radius or enter the Operator's Void Mode to escape it.

If a fully charged hacked Eidolon Lure is present near enough to the Teralyst, the lure will chain itself to one of the Teralyst's broken limbs. Each lure can chain itself up to maximum of two broken limbs. If there is a lure chained to the Teralyst, the players can continue the fight uninterrupted after a limb is broken. Without the lures, the Teralyst will teleport away, and the players will have to search for it again to resume the fight.

Stage 2
Once two weak points have been destroyed and the Teralyst is at 50% health it will begin two new attack patterns and modify one of the previous.


 * The first new attack pattern is it will charge up the arm cannon and proceed to fire directly into the air. A massive AoE will then begin where explosive projectiles rain down from orbit. These detonate upon colliding with the ground, but also have some homing capabilities, so staying airborne might help avoid nearby explosions, but not direct hits.
 * The second new attack is that the Eidolon Vomvalysts spawned around the Teralyst will launch exploding spheres similar to the large Aoe but with many fewer projectiles. This is best solved by simply keeping the number of Vomvalysts to a minimum which is also important because from once one or more limbs are destroyed, the Teralyst may scream and emit a blue light, which will cause nearby sentients to link themselves to the Teralyst and start regenerating its shields, with more Vomvalysts leading to faster regeneration.
 * Finally, the AoE fissure stomp where teal blasts pop up will begin to occasionally spread in a starburst pattern rather than merely circling from the front to the back. This pattern does not change until all weak points have been destroyed.

Stage 3
Once players destroy three weak points, the Teralyst will now attack more frequently, and will begin to fire off the seeking bullets attack often from the ground around it. It will begin to spawn the smaller sentients more often, and it is recommended to kill them quickly before they overwhelm the players.

Stage 4
After the final weak point is destroyed, the Teralyst will drop down and become invulnerable. At this point it will have roughly 20% health remaining. While downed, groups of Eidolon Vomvalysts will slowly gather to the Teralyst, healing it. The player should intercept and kill as many as possible. This will continue for several seconds. However, the Teralyst will no longer regenerate shields (except for its Regenerating Scream), and once this health bar is depleted, the Teralyst will die. During this phase it will behave similarly to stage three.

Once the Teralyst dies, it will collapse down onto the floor before slowly sinking away, dropping an Eidolon Shard as well as the Pummel, Full Contact, Crash Course, or Collision Force mods.

If the Teralyst is chained by two hacked and fully charged Eidolon Lures on death, its death animation is changed to display the Teralyst standing upright and floating in the air before sinking into the ground. To know that the Teralyst is ready for this specific kill, listen for the Quills' comment "Sentient energy contained. Act now." If successfully killed while chained, the Eidolon Lures tethered to it will explode and additionally yield four Intact Sentient Cores, two Exceptional Sentinet Cores, a Flawless Sentient Core, and a Brilliant Eidolon Shard.

Lures should be hacked by the host, as client lures often do not chain the Teralyst.

Tips

 * 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 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 Vomvalyst.
 * It is recommended that players that have Eidolon Lures following them should not be the main source of damage in the squad, as the lures seem to place themselves right in front of the player frequently, blocking shots and preventing the player from damaging the Teralyst.
 * If the Teralyst does teleport away, a light pillar will spawn shortly after which is visible in the plains for a moderate amount of time, this indicates Teralyst's next position. A Titania in Razorwing can easily fly up and identify the pillar.
 * Similarly, upon entering the fields, Teralyst will spawn along with their light pillars, which a razorwing Titania can easily spot.
 * 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.
 * If the Teralyst is still alive shortly before sunrise, it will walk towards the nearest body of water, become invulnerable, and disappear in a pillar of blue light as it sinks back in, preventing any further progress and forcing the player(s) to wait until the next night to fight a new one.
 * Multishot's additional bullets deal zero damage against the Teralyst's weak points.

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.