Undead potion

There should be a potion (maybe made with a mundane or thick potion) that causes potion effects to negatively effect the drinker, just like they do on the undead.  This obviously wouldn't work with things like Fire Resistance, which has no flip effect, but maybe it could remove the effect!  This could be especially useful in PvP - drink a night vision potion in a cave, and when your enemy comes near, drink the Undead potion to go invisible!  Or you could use it to effect your opponents with slowness but give yourself swiftness!