Unicorn

Unicorn is the transcendent support slime, and at 1 in 17.9 million it is a rare enough pull that most accounts see it as a late-game prize rather than a transit slime. With a Tier S profile it does more than buff, since it can fight too, which sets it apart from earlier supports like King.

Equip Unicorn when you want a slime that contributes on both sides of a hard run. After Pokey and SlimeSlime cover the raw damage slots, Unicorn rounds out the transcendent team with utility that Geode and your divine pieces simply do not provide. By the time you reach the ethereal tier, Unicorn is still earning its slot for the same reason.

Like most transcendents it is a commitment to chase, so only target it once your multiplier makes the odds bearable. Until Lucky and a deep luck stack are in place, Unicorn pulls feel arbitrary rather than earned. After that point, the support slot is solved for the rest of the climb, and Petal in the ethereals only takes over when an even rarer support is genuinely needed.