Sediment is a Nightmare Unique helm, hunted from The Mountain Sire once you are at Threat 20 or higher. 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 twice. 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, +14% Stone Damage, +22% Crumble Effect, +150% Crumble Effect, +148% Stone Damage, +404 Maximum Health and +129 Armor.

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.

It is Nightmare Gate loot.

“Layer by layer, everything becomes ground.”