In Act V of Diablo V, the Wanderer and their companions Lorath, Neyrelle, and Donan are all looking for a way to re-attune the soulstone of Astaroth for a new target. Donan is the only one who has the Horadric knowledge to do so, but it was his son whose life was taken by the very same soulstone – thus, he is trapped in a metaphorical Cage of Grief, the namesake of this Diablo 4 quest.
Taissa tells Lorath and the Wanderer that she worries Donan isn't emotionally strong enough to complete the process of repairing Astaroth's soulstone. The only option left is to force Donan to face his inner demons, and Taissa has just the concoction that will help him on that journey – but to make it, she needs Maggot Queen Ichor and Yellow Lotus Flower.
Maggot Queen Ichor Location
The first part of the psychedelic cocktail Donan must drink is Maggot Queen Ichor. Throughout the Hungering Swamp players will come across swarms of maggots writhing their way around the tunnels amongst the flies and other insects of the area.
Don't just start killing them randomly, though, as they only start to matter when killed in the highlighted area that appears when players get close.
Though the overworld of Diablo 4 is not randomized, many dungeons, cellars, and other instanced adventuring areas are. However, story dungeons are not randomized in Diablo 4, and the path to the Maggot Queen Ichor should be the same for all players.
From Taissa's hut, head to the west, then follow the main path southeast until a yellow circle appears on the minimap. Head into this circle, and start killing Maggots to summon the Maggot Queen. Kill her, then take the Maggot Queen Ichor back toward the hut.
Yellow Lotus Flower Location
The second part of Taissa's trippy tonic is Yellow Lotus Flower, which conveniently grows just north of her hut. From the entrance of Taissa's Hut, head north on either side, then continue to follow the path northward around a small loop. At the top of this loop, the Yellow Lotus Flower should spawn as a collectible item on the ground.
Walk over to the flower and pick it up, then head back to Taissa's Hut to turn both this and the Maggot Queen Ichor in. After a short bit of dialogue, one of the game's wildest – and most emotionally intense – sequences begins.
Diablo 4 is available for PC, PlayStation 4 and 5, and Xbox One and Series X|S