Stompy

Upon getting three items or pills that increase Isaac's size, he will create dust clouds when walking and have a chance to spawn rock waves around him upon taking damage.

Isaac can also crush rocks and other destructible obstacles by walking over them. Touching spiked rocks sometimes doesn't deal damage, depending on Isaac's size, speed and angle they're touched from.

Passive Collectibles

Name	ID	Icon	Quote	Description	Quality
Leo	5.100.302		Stompy	Isaac can destroy rocks by walking into them.	1
Magic Mushroom	5.100.12		All stats up!	Makes Isaac bigger. Adds one Red Heart Container, +0.3 Damage, x1.5 damage multiplier, +5.25 Range, +0.3 Speed, and restores all Health. Makes Isaac bigger. Adds one Red Heart Container, +0.3 Damage, x1.5 damage multiplier, +2.5 Range, +0.3 Speed, and restores all Health.	4

Pills

One Makes You Larger (each pill taken will count towards the transformation)

Notes

While the Thunder Thighs item does not contribute to the Stompy transformation, it still grants the ability to crush rocks and other destructible obstacles.
Picking up items that decrease size do not count against progress for this transformation.
This transformation makes it more difficult to effectively use Blood Donation Machines and Devil Beggars, as the rock waves will destroy them.

Trivia

This transformation and Adult are the only transformations that pills count towards.
This is the only transformation that doesn't add to Isaac's costume, and instead only changes his size and adds dust trails when he walks, as if kicking up dirt by stomping.