Shriekmaw

Mana cost: {4}{B}
Type: Creature — Elemental
Power / toughness: 3 / 2
Set: Murders at Karlov Manor Commander #139 (uncommon)
Price: $0.31 USD

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
When this creature 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.)

Shriekmaw has 17 printings, first in Lorwyn (2007). EDHREC ranks it #1,609 among Commander cards. It appears most in Ashling, the Limitless decks (20,364 on EDHREC). 9 public decks on TCG run it. It has 2 official rulings.

Legality

commander: legal
legacy: legal
vintage: legal
pauper: not legal
modern: legal
pioneer: not legal
standard: not legal
brawl: not legal

Public decks that run Shriekmaw

Counterpunch - Commander 2011, led by Ghave, Guru of Spores
Dance of the Elements - Lorwyn Eclipsed Commander Deck, led by Ashling, the Limitless
Deathdancer Xira - Magic Online Theme Decks, led by Xira Arien
Dungeons of Death - Forgotten Realms Commander, led by Sefris of the Hidden Ways
Enhanced Evolution - Commander 2020, led by Otrimi, the Ever-Playful
Plunder the Graves - Commander 2015, led by Meren of Clan Nel Toth
Plunder the Graves - Commander Anthology, led by Meren of Clan Nel Toth
Revenant Recon - Murders at Karlov Manor Commander, led by Mirko, Obsessive Theorist
Sworn to Darkness - Commander 2014, led by Ob Nixilis of the Black Oath

Commanders that run Shriekmaw most

Deck counts from EDHREC.

Often played with Shriekmaw

Cards that show up in the same decks on EDHREC.

Rulings

2021-03-19: 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.
2021-03-19: 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.