Marvel Super Heroes Commander

Creature — Cat

{3}{G}{W}: Monstrosity 1. (If this creature isn't monstrous, put a +1/+1 counter on it and it becomes monstrous.)
As long as this creature is monstrous, it has hexproof and indestructible.

Fleecemane Lion

Final Fantasy Commander

Legendary Creature — Human Elf Cleric

At the beginning of combat on your turn, put a number of +1/+1 counters equal to Maester Seymour's power on another target creature you control.
{3}{G}{G}: Monstrosity X, where X is the number of counters among creatures you control. (If this creature isn't monstrous, put X +1/+1 counters on it and it becomes monstrous.)

Maester Seymour

Tarkir: Dragonstorm Commander

Creature — Dragon

Flying
When this creature enters or becomes monstrous, exile up to two target artifacts and/or enchantments controlled by different players.
{4}{W}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)

Protector of the Wastes

Flying, haste, protection from white
{5}{R}{R}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)
When this creature becomes monstrous, it deals damage to each opponent equal to the number of cards in that player's hand.

Stormbreath Dragon

Duskmourn: House of Horror Commander

Artifact Creature — Toy

Indestructible
Whenever this creature attacks, blocks, or becomes the target of a spell, it deals damage equal to its power to each opponent.
{5}: Monstrosity 5. (If this creature isn't monstrous, put five +1/+1 counters on it and it becomes monstrous.)

Giggling Skitterspike

Modern Horizons 3 Commander

Hydra

Creature — Hydra

{X}{X}{G}: Monstrosity X. (If this creature isn't monstrous, put X +1/+1 counters on it and it becomes monstrous.)
When this creature becomes monstrous, create X X/X green Hydra creature tokens.

Hydra Broodmaster

Fallout

Creature — Lizard Mutant

Menace, trample
When this creature enters or becomes monstrous, destroy target permanent.
{5}{B}{G}: Monstrosity 4. (If this creature isn't monstrous, put four +1/+1 counters on it and it becomes monstrous.)

Alpha Deathclaw

Jurassic World Collection

Creature — Dinosaur

{10}{B}{G}: Monstrosity 10. This ability costs {1} less to activate for each creature with power 4 or greater your opponents control. (If this creature isn't monstrous, put ten +1/+1 counters on it and it becomes monstrous.)
When this creature becomes monstrous, destroy all artifacts and creatures other than this creature.

Grim Giganotosaurus

Jumpstart 2022

Snow Creature — Insect

{4}{S}{S}: Monstrosity 2. (If this creature isn't monstrous, put two +1/+1 counters on it and it becomes monstrous. {S} can be paid with one mana from a snow source.)
As long as this creature is monstrous, it has flying.

Chillerpillar

Creature — Rat Horror

{3}{B}{B}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)
As long as this creature is monstrous, it has menace. (It can't be blocked except by two or more creatures.)

Sinuous Vermin

{X}{G}{G}{G}: Monstrosity X. (If this creature isn't monstrous, put X +1/+1 counters on it and it becomes monstrous.)
As long as this creature is monstrous, it has trample.

Domesticated Hydra

Unfinity Sticker Sheets

Stickers

{TK}{TK} — Trample
{TK}{TK}{TK} — {3}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)
{TK}{TK}{TK} — 2/7
{TK}{TK}{TK}{TK} — 6/5

Jetpack Death Seltzer

Commander Legends: Battle for Baldur's Gate

Creature — Beholder

Whenever a creature an opponent controls attacks one of your opponents, double its power until end of turn.
{X}{X}{R}: Monstrosity X. (If this creature isn't monstrous, put X +1/+1 counters on it and it becomes monstrous.)
When this creature becomes monstrous, goad up to X target creatures your opponents control.

Death Kiss

Forgotten Realms Commander

Artifact Creature — Golem

{6}, Roll a d8: Monstrosity X, where X is the result. (If this creature isn't monstrous, put X +1/+1 counters on it and it becomes monstrous.)
Berserk — When this creature becomes monstrous, destroy target permanent.

Clay Golem

Commander Legends

Creature — Kraken

{6}{U}{U}: Monstrosity 4. (If this creature isn't monstrous, put four +1/+1 counters on it and it becomes monstrous.)
When this creature becomes monstrous, tap up to four target creatures. Those creatures don't untap during their controllers' untap steps for as long as you control this creature.

Shipbreaker Kraken

The List

Creature — Giant

Vigilance
{3}{W}{W}{W}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)
As long as this creature is monstrous, it has reach and can block an additional ninety-nine creatures each combat.

Hundred-Handed One

Creature — Octopus

This creature can't attack unless defending player controls an Island.
{5}{U}{U}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)
When this creature becomes monstrous, target land becomes an Island in addition to its other types.

Sealock Monster

Legendary Creature — Hydra

{X}{X}{G}: Monstrosity X. (If this creature isn't monstrous, put X +1/+1 counters on it and it becomes monstrous.)
When Polukranos becomes monstrous, it deals X damage divided as you choose among any number of target creatures your opponents control. Each of those creatures deals damage equal to its power to Polukranos.

Polukranos, World Eater

Creature — Crab

{6}{U}: Monstrosity 4. (If this creature isn't monstrous, put four +1/+1 counters on it and it becomes monstrous.)
As long as this creature is monstrous, it has hexproof. (It can't be the target of spells or abilities your opponents control.)

Skittering Crustacean

Creature — Cyclops

Trample
{5}{R}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)

Ill-Tempered Cyclops

Creature — Beast

Vigilance
{6}{G}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)

Ravenous Leucrocota

Commander 2020

Creature — Nightmare

Lifelink
{X}{W}{W}: Monstrosity X. (If this creature isn't monstrous, put X +1/+1 counters on it and it becomes monstrous.)
When this creature becomes monstrous, put a lifelink counter on each of up to X target creatures.

Vitality Hunter

Creature — Giant Soldier

Vigilance
{5}{W}{W}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)
When this creature becomes monstrous, exile all artifacts and enchantments.

Kalemne's Captain

Commander Anthology Volume II

{6}{R}{R}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)
When this creature becomes monstrous, creatures without flying your opponents control can't block this turn.

Stoneshock Giant

Conspiracy: Take the Crown

Copy

Creature — Ooze

{4}{G}{G}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)
When this creature becomes monstrous, create a token that's a copy of this creature. (The token has no counters and isn't monstrous.)

Splitting Slime

Creature — Gorgon

Deathtouch
{5}{B}{B}: Monstrosity 1. (If this creature isn't monstrous, put a +1/+1 counter on it and it becomes monstrous.)
When this creature becomes monstrous, destroy target non-Gorgon creature an opponent controls.

Keepsake Gorgon

Creature — Snake

Reach
{6}{G}: Monstrosity 4. (If this creature isn't monstrous, put four +1/+1 counters on it and it becomes monstrous.)

Nessian Asp

Commander 2015

Reach
{3}{G}{G}{G}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)
When this creature becomes monstrous, destroy target creature with flying an opponent controls.

Arbor Colossus

Journey into Nyx

{5}{R}{R}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)

Gluttonous Cyclops

Creature — Dog

{5}{R}{R}: Monstrosity 1. (If this creature isn't monstrous, put a +1/+1 counter on it and it becomes monstrous.)
When this creature becomes monstrous, it deals 2 damage to each opponent and each creature they control.

Wildfire Cerberus

When you're dealt combat damage, sacrifice this creature.
{4}{G}{G}: Monstrosity 2. (If this creature isn't monstrous, put two +1/+1 counters on it and it becomes monstrous.)
As long as this creature is monstrous, it has reach.

Swarmborn Giant

Creature — Cockatrice

Flash (You may cast this spell any time you could cast an instant.)
Flying, deathtouch
{5}{G}{U}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)

Fleetfeather Cockatrice

Theros

Legendary Creature — Gorgon

Deathtouch
{6}{B}{B}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)
When Hythonia becomes monstrous, destroy all non-Gorgon creatures.

Hythonia the Cruel

Creature — Elemental

{5}{R}{R}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)
When this creature becomes monstrous, each player sacrifices three lands of their choice.

Ember Swallower

This spell costs {1} less to cast for each creature card in your graveyard.
{7}{G}{G}: Monstrosity 5. This ability costs {1} less to activate for each creature card in your graveyard. (If this creature isn't monstrous, put five +1/+1 counters on it and it becomes monstrous.)

Nemesis of Mortals

Trample, protection from enchantments
{4}{R}{G}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)
Whenever this creature deals combat damage to a player, if this creature is monstrous, destroy target enchantment that player controls.

Polis Crusher

Defender, indestructible
{10}: Monstrosity 10. (If this creature isn't monstrous, put ten +1/+1 counters on it and it becomes monstrous.)
As long as this creature is monstrous, it has trample and can attack as though it didn't have defender.