The Dagannoth mother is fought at the end of the quest Horror from the Deep. She constantly cycles through different colours which blatantly show her weaknesses.
While fighting the Dagannoth Mother, do not hide behind the nearby stalagmites as she will disappear if she cannot engage you in combat and you will then have to start the entire fight over again. Protect from Missiles is advised as her Ranged attack is highly accurate. She can hit up to 160 LP with Melee, and can hit double 120s 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 avoid using rings of recoil or the Reflect ability.
Once she is defeated, you will obtain a rusty casket. Select the same option on the coffin twice (Saradomin, Guthix, Zamorak) in order to be rewarded with the corresponding god book.
The Gelatinnoth Mother fought during the last battle for Recipe For Disaster is based on her.
This version of the Dagannoth mother is one of the possible bosses available for a rematch at the Dominion Tower. Killing her there does not count towards a dagannoth slayer task.