Plotkai is generally a term used to describe a moment in bleach where a character in all rights should have died or something along those lines, but at the last second some random plot element saves them. Some examples would be Ichigo suddenly being able to defeat Grimmjow with ease because Orihime was crying or Rukia being saved from Grimmjow by the way-too-perfectly-timed appearance of Shinji.

Here, we call that Resolve Drive. Each player may use Resolve Drive to save themselves from death once per character. Your zanpakutou spirit might save you, or a strong NPC could show up and protect you. But that doesn't mean you get to start tearing things up as if it's okay to godmod all of a sudden!

The use of a plotkai is equivalent to giving up a fight. It will give you AR +2 for a single post which you may use to turn the tables and deal a blow against your opponent. But you may not kill or permanently cripple other players after using a Resolve Drive.  Since you cannot win, the most you could do is force a draw. The strain you body goes through by using up so much power leaves you unconscious and defenseless after the post. If you are in a thread not regulated by staff meaning it isn't a plot or mission thread, you may bypass this rule if the other rpers participating allow it. Note that when forcing a draw you don't necessarily lose the mission or fail a plot thread. But if there are more than just the one enemy to worry about or if you are in enemy territory fleeing might be the wiser choice. It is possible your character could end up captured or killed while unconscious. You would essentially be up to the thread master's mercy.

It will be possible to earn more Resolve Drives by participating in certain events, missions, or plot threads. However you may not possess more one use of Resolve Drive on a single character at any given time. This means you must gain it while not having one to save your behind. The other way you can gain resolve drive is if the thread master plans one for you. The player must be facing an NPC with 2 or more AR than the players involved. The thread master can grant a free resolve drive.