Castle Thorn

Death Breath

Tank: A conal fire breath at whoever holds aggro. Block it and hold her still, faced away; running her in circles only spreads fire.

Fire Spit and Stomp

All: She spits fire into the air that lands as static puddles across the floor. When she stomps, every puddle explodes; being in one at that moment is lethal, so stay out of them.

Stun Jump

All: She leaps onto a random player, often the furthest, and pins them. The others interrupt her immediately, or the pinned player dies.

Death Hound Broodlings

Tank: From roughly 75% health she howls up packs of broodlings. Taunt or pull them in so they stack on her.

Dps: They have low health; cleave them down without chasing around the room. Leaving one alive delays the next howl.

Dark Barrage

Tank: It fires a stream of purple bolts at one player. Step in front of the target and block to absorb them. On Veteran the target cannot survive it alone.

Shadow Strike

Tank: It vanishes and slams down on its target. Keep the taunt so the target is always you, and block.

Blood Channelers

Dps: Four scamps spawn along the sides of the room and beam power into the boss. Kill them together.

Blood Mines

All: Small red lumps appear on the floor after the channelers die. Do not step on them.

Blood Pool Phase

All: On a fixed 1-minute timer, it flies to the centre, becomes immune, and the lower floor floods with red ichor (can be skipped entirely with high group DPS). Move up and out; there is no damage outside it. Its shades then try to knock you back in, so gather in a corner, keep against the wall, and block the wing slaps.

Reanimated Vampire

Tank: A Reanimated Vampire spawns during the pool phase. Taunt it and turn it away.

Dps: Kill the Vampire before the boss returns to the floor.

Rend

Tank: A large overhead scythe swing that knocks down. Block it. Anyone else it targets must dodge.

Crow's Feast

All: A swarm of crows roams the arena as a large red circle and hits anyone nearby. Stay out of it, and lead it away from the group if it follows you.

Discard (Sickle Throw)

All: At 75%, 50% and 25% health he throws his sickle and everyone is dragged to it and stunned. On arrival each player gains a growing red circle. Spread out immediately with no overlap, or the combined burst is lethal.

Sickle Toss

All: Kill the animated sickle and stand in its green circle, then look up at a hanging corpse for a Use prompt to hurl the sickle at it. The body drops a Virulent Viscera that fights for the group. Optional, but free help.

Reanimated Vampire (Harvest)

Tank: After each Discard he raises a Reanimated Vampire. Taunt it immediately. Doorway strat: tanks can pull Vaduroth back into the entrance doorway to break line-of-sight on all reanimated adds, forcing them to stack tightly in group AoE cleave.

Dps: Kill the Vampire before returning to the boss. Pushing him too hard raises several at once, which is a wipe.

Virulent Viscera

Dps: His own purple ranged add, from Collection. Kill it quickly, then return to the boss.

Cross Swipe

Tank: A very heavy claw swipe that staggers and bleeds. Dodge roll it if you can, block it if not.

Gargoyles

Dps: He wakes the statues: fire gargoyles spit fire and cones, ice gargoyles walk in slowly with a growing effect. Move off the boss and kill each one as it wakes; Gwendis stuns them briefly. Then return to the boss.

Annihilate

All: He raises a hand and a blood beam locks onto a player's red circle. Move out of it. Below 50% the beam follows its target, so lead it away from the group and have everyone split.

Disintegrate

All: Below 50% he gathers a blood storm and slams it into a large red circle that lingers. Move out of the impact and stay off the residue.

Volatile Hound

Dps: When he shouts, a Volatile Hound spawns nearby. Kill it before it reaches the group.

Heavy Attack

Tank: An enormous hit. Block or dodge it every time; unblocked, it kills the tank outright.

Incursion (Charge)

All: She turns invisible and dashes across the floor into one player, usually the furthest, to drain them. Block or dodge roll it, or it is lethal.

Rive and Expulse

All: Bomb effects on the ground that either detonate in place (Rive) or are pushed outward in lines (Expulse), stunning on hit. Step out, then return. Below 50% Rive becomes a single growing circle she casts instantly.

Batswarm: Green Safe Zone

All: From roughly 90% health, bats cover the whole arena with escalating damage; one green circle is the only safe spot. Get into it quickly and fight her from there.

Scatter

All: At roughly 70% and 45% health she bursts into a swarm: a large damaging area where she stood, small swarms firing outward, and Blood Crawlers pouring out. Avoid all of it and kill the crawlers. The small swarms then converge where she will reappear; standing there is instantly lethal.

Blood Dive

All: During the swarm she dives in a straight line, knocking back and stunning. Block it to avoid the crowd control.

Invulnerable Phase (55% and 15%)

All: At 55% and 15% health, Lady Thorn flies into the center, becoming invulnerable as bats shroud the arena. Stay inside the moving green protective circle. Kill the Blood Scavengers: each leaves a Corrupted Blood puddle granting a throwing synergy. Exactly 4 synergies are required per intermission (1 per group member for the "Taking Turns" achievement) thrown at Lady Thorn to break her shield and bring her down.

Blood Guardian (Hard Mode)

Tank: A large Blood Guardian appears in the swarm during the invulnerable phases. Taunt it and interrupt its channeled effect.

Dps: The Guardian must die before the next one spawns, and more zombies are in the room. The circle also moves faster on Hard Mode.

Execute in the Dark (Hard Mode)

All: After the 15% phase the batswarm never clears. She is targetable again, but the rest of the fight happens inside the moving green circle, dodging bombs and blocking charges and heavy attacks. There is no DPS check; stay in the light.