Its a bit of a debate how powerful this card will be its Tranquil Flower ability provides consistent healing every turn, although it can be negated by the always prevalent Path to the Peak card
Incapsula incident ID: 1532000690248601983-442346494460957006
Out of the few dozen that exist from various sets and expansions, the best are the ones that can dish out the most damage as well as possessing useful secondary effects and granting a generous amount of maximum HP
Vivien, Monsters' Advocate makes great tokens that can adapt to offense or defense, and you can have some degenerate turns if it lives long enough to -2
I would also consider one or two copies of Arabella, Abandoned Doll, which rewards you for going wide with small tokens while acting as a Gleeful Demolition target if the need arises
For the most part, trying to stay Dimir is ideal and lets you draft the necessary pieces for your deck when they show up, but on a draft-by-draft basis, you want to be aware of the reasons to go into additional colors