Round 1 challenges (4 units):
Edit: all the Mephits are supposed to be Rare, not Common...

Round 1 bonus submission (4th challenge unit):

Just to clarify: each Trigger has its own cost of 2 Value, so all 4 summons upon moving to the Ability Target will cost 8.

It has to be said, though, that this piece would require some additional AI so that it could purposefully use its Triggers...