Reveillark death trigger
It's not necessarily the stack that you need to figure out, it's triggered abilities and abilities resolving.

Here's what happens.


Opponent casts Wrath.
Wrath resolves, placing your creatures in the graveyard.
Reveillark's ability triggers. Since it and the other creatures are already in the graveyard, they are legal targets (well, not the Reveillark itself)
Reveillark's ability resolves, returning the other two creatures.