Beasts here can't be targeted by enemies.
Does this prevent enemy magic from harming my beasts?
Yes, as long as the effect says 'target'. You'll need to bring in a specialized exterminator to flush out these hidey-holes.
What counts as an 'enemy' for this effect? Is it enemies of the beast, or enemies of the site?
Beasts at Varmint Warrens cannot be targeted by spells or abilities used by the enemies of the beast. All kinds of critters can hide in the warrens!
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