叫び大口

畏怖（このクリーチャーは、アーティファクトでも黒でもないクリーチャーによってはブロックされない。）
叫び大口が戦場に出たとき、アーティファクトでも黒でもないクリーチャー１体を対象とし、それを破壊する。
想起{1}{B}（あなたはこの呪文を、これの想起コストで唱えてもよい。そうしたなら、これが戦場に出たとき、これを生け贄に捧げる。）

Shriekmaw

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
When Shriekmaw enters, destroy target nonartifact, nonblack creature.
Evoke {1}{B} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Murders at Karlov Manor Commander

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
When Shriekmaw enters the battlefield, destroy target nonartifact, nonblack creature.
Evoke {1}{B} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters the battlefield.)

Forgotten Realms Commander

Time Spiral Remastered

Commander 2020

The List

If you pay the evoke cost, you can have Shriekmaw's own triggered ability resolve before the evoke triggered ability. You can cast spells after that ability resolves but before you have to sacrifice Shriekmaw.

To determine the total cost of a spell, start with the mana cost or alternative cost you're paying (such as an evoke cost), add any cost increases, then apply any cost reductions. The mana value of the spell is determined by only its mana cost, no matter what the total cost to cast that spell was.