The Gelatinnoth Mother is a monster encountered during the final battles in the Recipe for Disaster quest. She is the equivalent to the Dagannoth mother from the Horror from the Deep quest, although Gelatinnoth Mother will switch colours after a certain amount of damage/hits is dealt. She will turn different colours every 15 to 20 seconds, not counting damage/hits dealt in the current colour, and her colour shows her weakness to a certain type of magic spell or attack.
The Gelatinnoth Mother is fight-able as a boss monster in the Nightmare Zone minigame if the player has completed Recipe for Disaster.
The following table shows her colours in the order she cycles through them in the Defeating the Culinaromancer subquest and lists which attacks she is weak against in each state. You can safe spot the Gelatinnoth Mother at the corner of the arena and wait until the colour of your choosing to attack her.
Players are faced with a dilemma on this monster, as they must defend against both melee and ranged attacks without using prayer, but be able to attack most of the time using magic. The challenge is to find a mix of armour that provides sufficient defence without imposing undue attack penalties.
A good set of armour is full Ahrim's with an Air staff and an Obsidian shield, as this gives players a respectable mage attack bonus (which players need two-thirds of the time) and also allows players to have a balanced defence against the mother's attacks. Using high class melee armour such as Barrows even while using spells at 65+ Magic still works perfectly fine, as long as players use attacks to which the Mother is currently weak and which negate virtually all of her ranged damage throughout the encounter. (Players should still bring some high-healing food, however, for her melee.) Tested success rate with spells using this armour at level 68 Magic was roughly 80% when using the appropriate elemental spell.
Another great way to get through this fight is with Void Knight equipment. You can cycle through powerful melee, magic, and ranged armour by exchanging the helms. The armour also gives a good defence against all types of attacks.
A slightly less exotic armour mix that works is a mage top and bottom (such as Skeletal armour, Splitbark armour, or Lunar equipment), a Helm of neitiznot or Dragon helm, and a Rune kiteshield. This combination still has a significant ranged attack penalty, but players can wait until the Mother switches vulnerabilities to begin attacking again.
If a player has 70 Ranged and 60 Defence, it's quite easy to maximise range and mage defensive bonuses. Using a combination of a Mystic robe bottom, Black d'hide body, Dragon sq shield, Farseer helm, God capes, Dragon gloves and an Amulet of fury, as this provides decent mage attack bonus, and very good all around defensive bonuses.