Death

Upon reaching zero health, Warframes will go into a bleedout state, which is a twenty-second period of dramatically-reduced combat capability, only being able to use secondary weapons. If the Warframe is not revived during this time, it dies a proper death and must either spend 10% of their Affinity acquired during the mission to continue playing the mission, wait for an ally to finish the mission, or forfeit the mission entirely. Players are only allowed to revive 4 times per mission, barring special circumstances.

Bleedout will not trigger if there are no other friendly Warframes present that are not themselves bleeding out (note this includes playing in Solo mode). Running out of health in this circumstance will cause immediate death with no bleedout. This exception itself has an exception: if The Grustrag Three are present in a mission, running out of health will always trigger bleedout, even in Solo play.

Bleedout

 * Not to be confused with Bleed, the status effect.

Warframes in this state have fallen down to the ground, barely able to shuffle around backwards on their posterior and feet. While bleeding out, Warframes cannot use abilities or perform maneuvers, and can only fire their equipped secondary weapon. Downed Warframes appear as a red diamond on the mini-map and slowly bleed out over 20 seconds.

Process
You can revive these Warframes by holding the action key while nearby and facing them. This action takes priority over most other player input: if you sprint towards the downed ally while holding down the action key, you will automatically stop running and start the revival process (this is immensely useful during Archwing missions, where precise movement is difficult). While being revived, a red diamond will appear to replace the red downed-state bar and begin to fill. Multiple teammates reviving another at the same time speed up the process. Once the revival bar is full (which takes 5 seconds by default), the downed Warframe is revived to full health and shields and may resume using all equipment and powers as normal. Successful revives performed onto other players are tracked by the end-of-mission leaderboard. Tenno downed by The Grustrag Three will be captured by any living Carabus Sentinels, and cannot be revived by players while contained.

Safety
When reviving an ally in the heat of battle, it's advisable to take care not to be downed yourself. The use of crowd-control effects is valuable for safe revival; otherwise, it's very common for players to be downed at the exact moment they've successfully revived a teammate. The Sentinel mod Sanctuary creates a damage-absorption bubble around you while you revive fellows. Ash's Smoke Screen, Ivara's Prowl, Shade's Ghost, Loki's Invisibility, and Limbo's Rift Walk all allow you to revive without issue. Be careful to position yourself not to block your fallen ally's line of sight; sidearms are just as powerful while bleeding out, but they cannot punch through Tenno. A Warframe in bleedout might actually be able to do more damage if they have Provoked equipped, as it amplifies all damage done while bleeding out, including the continuing damage of abilities cast before being downed.

Timer
The 20-second bleedout timer can be extended by two effects: Undying Will and Renewal. Undying Will is a Warframe mod which, at max rank, increases bleedout time to 28.4 seconds. Renewal is Oberon's ability which will extend the bleedout timer by 45% before Power Duration effects&mdash;it is possible to cause the bleedout timer to run backwards with enough Power Duration. In both cases, these effects are not reflected in the red bleedout timer text above players' heads; these effects instead increase the amount of time it takes for one second to pass by.

If there are no means for you to be revived (you are playing solo mode, or all other cell members are bleeding out or dead) when you run out of health, you skip the bleedout phase and are immediately dead (with the partial exception of Inaros; see below). Sacrifice, which causes the player's sentinel to prevent Warframe death at the cost of its own life, would have been a highly desired mod to help solo players do well, but it was an accidental release and can no longer be obtained.

Abilities
Warframes can also be revived from bleedout by a few special circumstances. The most explicit special case is the Soul Survivor Augment for Nekros's Soul Punch; it allows Nekros to revive allies from range at the expense of draining all of his energy. The Phoenix Renewal Augment for Oberon's Renewal is similar in that allies that take fatal damage while under Renewal's effects will instead be healed a percentage of their health, though this effect will only work once per ally. Trinity's Triage Passive ability allows her to revive allies 25% faster than other frames and from a further distance, making it easier for her to bring someone back to the fray.

Inaros and Nidus possess the Undying Passive ability, albeit with different effects, that trigger when they would normally enter a bleedout state. Inaros enters an immobile sarcophagus upon losing all his health. In this state, Inaros can drain health from nearby enemies or allies, which contributes to the revive bar, and once the revive bar is filled, Inaros revives on the spot. For every 1% of health drained, the revive bar is filled by 0.5%, thus Inaros will need to drain at least 2 enemies of their health in order to revive. Although this ability is active even in solo play, allies can revive him as normal, and if there are no enemies present for Inaros to drain health from (or the enemies have too much health to drain in time), Inaros will die of bleed out like normal. Nidus, however, will not enter a bleed out at all if he has at least 15 stacks of Mutation/Adaptation Stacks. Instead, 15 stacks will be substracted from his total stacks, and he will become invulnerable for 5 seconds and regenerate 50% health. If he does not have 15 stacks when his health reaches 0, he will lose all current stacks and bleed out like normal.

The New Moon passive of the Vazarin Focus grants a set of instant revives when the Focus is activated during the mission, allowing the Focus's caster to quickly bring an ally back on his or her feet. Lastly, in the event that you are healed at the moment of hitting 0 HP (by falling down onto a Health Orb, for example), you will be revived to full health nearly instantly, with only a mere interruption to your action at time of death and a message broadcast to all cell members that you were revived.

NPC Bleedout
Aside from players, there are some NPCs (non-player characters) that have bleedout phases. Kubrows can be revived by any players who find them while they're bleeding out, but though they are marked on the mini-map as a red diamond, there is no center-screen text notification alerting teammates. Rescue targets can be downed while you are escorting them to extraction; they have a bleedout period during which you may take out enemies and safely revive them afterwards. Sentinels cannot be saved from bleedout from all practicality, but on occasion a player might notice the bleedout text and red diamond on the mini-map for a fraction of a second before the sentinel explodes irreparably. Enemies do not bleed out at all, although Capture targets writhe around on the ground instead of being turned into a corpse object&mdash;fortunately, they cannot shoot, scoot around, or be revived from that state. Syndicate Operatives will also go into bleedout and can be revived, however their timer, while not shown, is shorter than players'. The operatives can also revive each other, but cannot revive fallen players.

Death
Death occurs after the bleedout timer counts down to 0 seconds. Presumably, your Tenno doesn't actually die&mdash;because there are almost zero permanent consequences for death other than the failure of the mission (if you choose not to revive) and the losses associated with that&mdash;but he or she is still neutralized as far as the enemy is concerned.

During Death
While your Warframe lies dead on the ground, you are able to watch your fellow cell members continue on with the mission, and are given the options to revive your Warframe or abort the mission. If you elect to do neither, you can still complete the mission if another player finishes the objective and makes it to extraction. Be warned that if you have spent more than 2 minutes idle (you cannot be anything but idle while dead on the ground) while the mission is being finished, you do not receive the end-of-mission bonuses like credits, bonus affinity, and alert rewards; you keep in-game pickups and other affinity gained during the mission from activity. Dying will also have a chance to drop pickups similar to enemies, like any ammo type or energy.

When sentinels die, they might drop loot for you if they have Spare Parts equipped; you can double-dip if they have Regen equipped. On the other hand, if your Kubrow is killed in battle before you are, they lose happiness; if you are killed before your Kubrow, they do not.

Enemy Corpses
Dead enemies, from a technical perspective, are flagged as corpses and are subject to certain mechanics in that state. Most obviously, Nekros can Desecrate enemy corpses, treating separated body parts as separate corpses; this leads to players 'desecrating' corpses with damage weapons before the Nekros can use their desecrate ability. Some enemies do not leave corpses, such as the Stalker.

There exist objects in the world that take the form of already-dead enemies, but these corpses are more like lockers (you press the action key to loot them) and do not interact like normal corpses.

Revives
If they choose to revive, the Warframe spends 10% of their acquired Affinity from the mission in progres and will rise up to release an energy blast that deals, , and damage, knocking over nearby enemies. The Warframe will then be temporarily invulnerable. If you chose to forfeit, you have a chance to reverse your action by pressing and selecting the appropriate option. If a player's teammates are still alive, the player will enter a spectate mode. Choosing to forfeit allows you to spectate your team making it easier to see if you want to spend a life, which is good if you or your team is not geared enough for the mission.

By default, a player can only revive 4 times per mission. However, fully ranked Arcane items each grant 1 additional revive, for a maximum of 6 revives. Furthermore, new players during the Vor's Prize quest are instead given 12 revives during said quest.

When reviving, dead companions come back to life. Some players intentionally die and revive in order to bring back their companions for their useful long-term utility.

Bugs

 * Movement can prove to be cumbersome during Bleedout. Shuffling backwards doesn't always respond properly, and you can easily get caught on strange terrain.
 * If all living teammates make it to the extraction zone while a player elsewhere bleeds to death, the living must step out of the extraction zone and back to trigger the extraction sequence and the end of the mission.
 * Oddly, Syndicate Death Squads will keep the player alive in a downed state even whilst playing solo, despite having no further interaction with them unlike the The Grustrag Three or the Zanuka Hunter.
 * For unknown reasons, sometimes a Tenno can revive themselves using Affinity, even if they have no revives left. This will cause the revive counter to begin counting into the negatives, and allow the Tenno experiencing the glitch to have infinite revives, as long as they have the affinity to pay for it.