Crumbling Ashes

At the beginning of your upkeep, destroy target creature with a -1/-1 counter on it.

Soul-Scar Mage

Prowess
If a source you control would deal noncombat damage to a creature an opponent controls, put that many -1/-1 counters on that creature instead.

Necroskitter

Wither (This deals damage to creatures in the form of -1/-1 counters.)
Whenever a creature an opponent controls with a -1/-1 counter on it dies, you may return that card to the battlefield under your control.

Blazing Volley

Blazing Volley deals 1 damage to each creature your opponents control.