Titan Stealing

Titan Stealing is when a player eats (kills) a Titan Shifter to take their titan, like we see in Attack on Titan. This functionality is in the pack, but disabled by default (because origins are meant to be rather permanent). In the config, the "Stealable" option under Titan Stealing will make titans non-permanent. This means once a titan is selected from the Origins menu, it gets automatically disabled (it'll be re-enabled if the player loses the origin), but other titans (all of this is configurable) can steal that titan by killing the player that chose it.

That same configuration option also lets you restrict titans to one per player.

Titan Stacking is also in the pack, which can only come into effect when Stealing is enabled.