Sediment is a Nightmare Unique helm, hunted from The Mountain Sire in the Mortal Arena, always at item level 120. It is one of four Exceptional drops on its list — 2.5% of the Uniques that boss gives up, about 1 in 40 — and every kill rolls the list 5 times. It is built on Sovereign Stonegaze Helm — step 6 of the Stonegaze Helm line, item level 80 and up.

It always rolls the same numbers: +72 Armor, +327 Maximum Health, +14% Stone Damage, +22% Crumble Effect, +45% Crumble Effect, +48% Stone Damage, +491 Maximum Health and +218 Armor.

One Unique drop in 40 is a Mythical copy: the same item carrying 15–25% Mythical Energy that boosts every stat on it and can never be changed; the 15% floor is 10 times as common as the perfect 25%.

On top of that it carries Sediment — Your Main is attuned to Stone and every hit heaps Crumble; Sunder cracks the ground in a Seismic shockwave and your blows shove harder, but hit 10% softer.

It leans into Stone and Crumble.

“Layer by layer, everything becomes ground.”