The Transformed Animal Omni Schtick "Magic Drain" is intended for use by Transformed Animal PCs vs sorcerous / supernatural GMCs. (It is, after all, in the section with hero Schticks, not the section for Foe Schticks.)
The power as written says:
Magic Drain After a successful attack against a character with more than 0 Magic points, spend 1 Chi and 1 shot as an interrupt. Target loses 1 Magic point.
The problem, of course, is that GMC sorcerers don't have Magic points. Only PCs have Magic points.
Rather than just throw the Schtick out the window as useless, I'm considering House-Ruling it instead. Instead of zapping a non-existent GMC resource, I think I'll reword it as:
Magic Drain After a successful attack against a Sorcerer, Ghost or Supernatural Creature, spend 1 Chi and 1 shot as an interrupt. The target suffers 1 point of Impairment for the rest of the scene. If the target has Magic points, they also lose one Magic point.