What does Helmwhelp evolve into?

You need level 48, a Blaze Stone and a Perfect potential Helmwhelp to get Infergon.

The potential rule is the one that stops most players. Good or Elite quality is not enough, and Infergon cannot be caught in the wild, so evolving is the only route. Perfect stats carry over through evolution, which makes the practical plan simple: catch around 20 to 30 Jawling, keep the Perfect one, and raise that. Mountain form Jawling spawns in set places, including inside a crack in the floor near the Sanctum First Site ruins in the Russet Highlands.

How to evolve Helmwhelp into Infergon

Evolving into Infergon happens at the sword and starts a fight with Omega Infergon, which you must win. That arena sits at the end of the Russet Highlands Warrior story quest, part of the main storyline that begins with a helmet quest from Painter Sora. Omega Infergon becomes fightable when you return to the arena after that quest is finished. Like every Omega boss, it cannot be captured, so beating it is purely the unlock.

The Jawling puzzle and questline are also in the Russet Highlands. The entrance is under a pile of leaves behind ruins on the northern cliff of the Sanctum First Site.

What Infergon does once you have it

Infergon is a Fire-element DPS and the natural main damage dealer for a fire team against bosses. Flaming Claws is its main damage skill, and Lava Breath applies eight stacks of the Fire debuff to its targets. Ferocious Fang is the recommended held item. It also flies, with the Fly III traversal ability.

A Prismana Infergon exists separately as a Season 1 reward: an egg earned through stamps in the Season Journey on reaching season rank 12.