Love is in the Lair

Before the boss room, locate two interactable items: the Box of Candy is found at the bottom of the staircase in the crossroads area to the left on the railing, and the Anub'arash Plushy is found on the left side of the door frame at the entrance of the path to Ky'veza. Two different players should pick up one item each, as looting an item grants that player the action button to throw it.

Before pulling the bosses, use your extra action button to throw the Anub'arash Plushy at Anub'arash (granting him the Anub'arash Plushy buff) and throw the Box of Candy at Skeinspinner Takazj (granting him the Takazj's Favorite Candy buff). This must be done before combat begins, as the items cannot be thrown during the fight.

Once you pull the Silken Court, the bosses will gain the Bond of Friendship and the achievement criteria will be active. Keep Anub'arash and Skeinspinner Takazj separated throughout the fight, as they heal for roughly 1% of their maximum health per second whenever they are stacked together. Some mechanics such as Anub'arash's charge and Takazj's pull will briefly force them together, so tanks should split them apart again as quickly as possible.