How does a Loyal Cathar react to Undying Evil?
It would come back as Loyal Cathar with a +1/+1 counter on it.

Undying Evil's triggered ability returns Loyal Cathar to the battlefield upon dying, Loyal Cathar's triggered ability sets up a delayed triggered ability that returns the card "at the beginning of the next end step".

Loyal Cathar's normal return-to-battlefield trigger won't find the card in the graveyard when it resolves, so will fail to do anything.


  603.7c A delayed triggered ability that refers to a particular object still affects it even if the object changes characteristics. However, if that object is no longer in the zone it’s expected to be in at the time the delayed triggered ability resolves, the ability won’t affect it. (Note that if that object left that zone and then returned, it’s a new object and thus won’t be affected. See rule 400.7.)