Normal Hard

The Dagannoth mother is fought at the end of the quest Horror from the Deep. She constantly cycles through different colours to explicitly show her weaknesses.

While fighting the Dagannoth Mother, it is possible to hide or safespot behind the nearby stalagmites. Protect from Missiles is advised as her Ranged attack is highly accurate. She can hit up to 16s with Melee, and can hit double 12s with Ranged. Pures are advised to bring a ring of recoil and turn off auto-retaliate if not using melee. It should be noted that if she is killed by any source of recoil, the player will have to leave the area and repeat the fight (this may be a glitch). As a result, players should unequip their rings of recoil when she has low health.

Once she is defeated, you will obtain a rusty casket.

She can be fought in the Nightmare Zone after the quest is complete. Runes are provided in the arena.

Punching her is ineffective as she will regenerate life in her immune forms quicker than you can damage her. 

Weakness by colour

Image Colour Weakness Attack Using
Dagannoth mother white White Air spells Wind Strike, Bolt, Blast, Wave, Surge. Bringing Chaos gauntlets may be a cheaper alternative while still being effective during the fight; as Bolt spells would hit one under their Blast counterparts.
Dagannoth mother blue Blue Water spells

Water Strike, Bolt*, Blast*, Wave, Surge.

Dagannoth mother brown Brown Earth spells Earth Strike, Bolt*, Blast*, Wave, Surge.
Dagannoth mother red Red Fire spells Fire Strike, Bolt*, Blast*, Wave, Surge.
Dagannoth mother orange Orange Melee Melee attacks.
Dagannoth mother green Green Ranged Ranged attacks.

Community content is available under CC-BY-SA unless otherwise noted.