Ancient Stag of Mossfells is a level 36 boss in Mossfells. This guide covers the fight in solo and in 6-player co-op, with phase-by-phase strategy and the loot table.

Optional but drops the best broom upgrade material.
Emberkin is the best Coven for the Ancient Stag of Mossfells fight thanks to its single-target burst. Mirewarden is the second-best pick for solo — its self-heal covers the biggest damage windows in phase 2.
The Ancient Stag of Mossfells uses basic melee and a ranged spell. Dodge-roll through the spell (it has a clear telegraph) and use the gaps to land 3–4 hits. Save your cooldowns for phase 2.
A new attack pattern starts. Ancient Stag of Mossfells applies a stacking debuff — cleanse it at your Hearth or use a Mire-Cure Potion. At this point, your Coven’s signature spell is your biggest damage tool. Use it on cooldown.
Ancient Stag of Mossfells summons adds. Keep the Hearth Hound on the adds and burn the boss. In solo play, the safest pattern is to kite adds around the arena while landing ranged attacks.
On Hard mode the Ancient Stag of Mossfells has +50% HP, +25% damage, and one extra attack per phase. The unique cosmetic drop is Ancient Stag of Mossfells’s Visage, a head-piece with a unique particle effect.