msem-instigator

Creatures you control attacking cause abilities of that creature to trigger as though it entered.
Once each turn, when you attack, you may pay {1}{R/W}. When you do, untap target attacking creature. After this phase, there is an additional combat phase.

When Overgrowth Guardian enters, germinate. (Put a +1/+1 counter on a creature or create a 1/1 green Saproling creature token.)

Flash
When Qililia's Scavenger enters, look at the top six cards of your library. You may put a Merfolk card with lesser mana value from among them onto the battlefield. Put the rest on the bottom of your library in a random order.
Other Merfolk you control get +1/+1.

Improve {1} ({1}: Put a +1/+1 counter on this creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)
At the beginning of your upkeep, exile up to one target nonland permanent you own. Return that card to your hand. If Soul Reader has two or more counters on it, you may instead return that card to the battlefield under your control.