msem-instigator

(As an Encounter enters, choose an opponent to protect it. You and others can attack it. When defense counters are removed, create a 0/0 Army token if you don't control one, then put that many +1/+1 counters on a Army you control.)
When A Matricide Most Foul enters or is defeated, each opponent exiles a permanent they control with the highest mana value among nonland permanents they control.