when the sheep debuff is placed on a champion, they are turned into a sheep. while in the form of a sheep, they lose all active and passive abilities. they are replaced by a single ability, which is "attack 1 enemy. all allies who are sheep join in the attack. after attacking, has a 50% chance to remove the sheep debuff from this champion" (i've only dealt with it a few times so i may not have the details 100% accurate, but you get the gist of it).

sheep debuffs are protected so a cleanser won't be able to help you. the champion can be returned to normal in one of 3 ways; waiting 2 turns for the debuff to expire, being removed by the ability mentioned above, or having the sheep reduced to 0 health. in all 3 cases, the polymorphed champion will be returned with 50% health.

Thanks for this excelent explanation.  Just what I needed.  If you can't kill the target, then I suppose the strategy is to wear down or kill the other members. I guess it would be useful in arena or doom tower regular rooms. but I'm not sure who I would want to put it on.

This is the first result in Google and doesn't say anything about how this is placed. Really good explanation....

If the champion has a Polymorph blessing, it is placed as below:

Has a chance of placing a [Sheep] debuff on enemy Champions for 2 turns whenever they place debuffs on this Champion or remove or steal buffs from them. This debuff cannot be blocked or resisted