Because why not.
Similar to Seduce, the player loses control of their character and will follow and attack other players in their expedition. Can be dispelled and wears off after a bit.
Player becomes possessed by a ruthless and vengeful spirit. The player can only rid himself of the curse by attacking and dealing enough damage to another player. Barring that, the afflicted player will die in 20 seconds and the ghost will possess another living character. However, other characters are allowed to attack the player to dispel the ghost, who will leave the fight once the afflicted player dies. Casting Heal will banish the ghost. The ghost lasts 60 seconds if not killed, meaning it can take over up to three players.
Similar to the above, but the boss itself jumps into a player while the player controls the boss, similar to that boss PvP nonsense. Jump + Direction becomes teleport if the particular boss can do that. On the afflicted player's screen, a UI appears telling him or her what keys activate what skill. if the boss' body takes too much damage, the player will die. The bodies will revert back to their proper owners soon enough.
The afflicted character will start to float in the air as if they were swimming. Ranged character attacks no longer automatically curve to hit their target. Player will slowly rotate while suspended in midair, making aiming difficult.
Player becomes petrified in stone and will inch his or her way to death unless every other party member attacks him or her at the same time.
MP Consumption for all skills is quadrupled.
The player's morale is crushed and they are forced to act drastically. Attacks will now consume HP rather than MP.