Mustrum_Ridcully
Legend
I like the idea of the sustain requiring an attack. It also introduces an interesting decision point for the "trapped" monsters - they have to decide whether they want to get out or keep hitting their enemies.
Other escape ideas: Trying to escape requires a basic attack against the wizards will defense. The target is either the orb or the borders of the terrain. On a success, a creature can leave.
The topology of the orb might also be less usual - instead of a simple square, it could actually on a four-dimensional torus, so if you go out south, you go in north. This makes it a lot harder for the Wizard to protect himself from attacks. So you really shouldn't take too many enemies with you...
Other escape ideas: Trying to escape requires a basic attack against the wizards will defense. The target is either the orb or the borders of the terrain. On a success, a creature can leave.
The topology of the orb might also be less usual - instead of a simple square, it could actually on a four-dimensional torus, so if you go out south, you go in north. This makes it a lot harder for the Wizard to protect himself from attacks. So you really shouldn't take too many enemies with you...