Magmaargh

Magmaarghs are a variant of Blarggs that first appeared in Super Mario Galaxy 2. They appear as large molten lava creatures with a huge mouth that attack by rising up from lava pools and biting down at anything in front of them. Like their relative the Magmaw, they seem to be mostly liquid, as they can pass through solid objects.

Super Mario Galaxy 2
They mostly appear in Melty Monster Galaxy, being the titular monster. They also appear in Fleet Glide Galaxy and Bowser's Galaxy Generator. Magmaarghs do not move very much, mostly staying under the lava, arising to chomp down on anything in front of them. If Mario or Luigi gets chomped he loses one wedge of health. In the Melty Monster Galaxy, they appear mostly where there are Pull Stars. In Bowser's Galaxy Generator, 3 of them appear during the Snake Block section. Here, the Snake Blocks split into 2 paths, where there is one Magmaargh per path and when the Snake Blocks come back together, one last one appears, where Mario (on Yoshi) must swallow a nearby Blimp Fruit to pass over the monstrous creature (or he needs to go out of the way onto one of the four platforms if he already lost it).

Super Mario 3D Land
Magmaarghs later return as enemies in Super Mario 3D Land; they only appear in the lava pools of World 8-Bowser: Part 1 and Special 8-Bowser, passing perpendicularly through Mario's path. In this game, they are much smaller than in their first appearance. Magmaarghs cannot be defeated, even if the player is invincible. Sandmaarghs, sand variations that follow Mario or Luigi underground and pop out to chomp them, also debut in this game.

New Super Mario Bros. U
Magmaarghs return in New Super Mario Bros. U. They only appear in Iggy's Volcanic Castle, during the boss battle. Iggy can fire special red magic beams with a skull design on them. First three beams appear, two green, one red; then when Iggy is hit he will fire five of them, three green, two red; and when Iggy Koopa is stomped twice, he manages to fire twice. When Iggy Koopa fires a red magic beam at the lava, the Magmaargh will emerge from it. The Magmaargh then attacks by moving towards the players in a wave-like movement. Magmaarghs, Cheep Chomps, and Magmaws are the only enemies who can defeat Nabbit, a playable character in New Super Luigi U.

Super Mario 3D World
While Magmaarghs themselves didn't appear in Super Mario 3D World, nor did they appear in Captain Toad: Treasure Tracker, a subspecies that attack by jumping out of lava at any of the five characters called Charvaarghs, appear. They were introduced in Super Mario 3D World.

Mario Party: Star Rush
Magmaarghs make an appearance in Mario Party: Star Rush, appearing as obstacles in the minigame Lava Labyrinth.

Trivia

 * In the files for Super Mario Galaxy 2, they are known as "Unbaba," the Japanese name for Blargg, which they shared an attack pattern with at the time. However, in subsequent games where their attack pattern is changed, the filename is changed to "WooGan," a romanization of its Japanese name.