Millicent, Restless Revenant isnt the most synergetic spirit commander, but this Azorius card does have its value
(Equipment, Auras you control, and counters are modifications.) The +1/+1 counters on Costume Closet won't affect it unless it somehow becomes a creature
In a worst case scenario, you test them out in a few games, replace them with other cards, and learn a little more about how your deck functions in the process
Though it has a high casting cost, Revel In Riches is a fantastic card that gives you Treasure tokens just by killing your opponents' creatures which black is best at doing thanks to the plethora of removal available in the color
Other deck archetypes will benefit too, but these are two that will receive the biggest uplift to bring them back into the meta.
Inside the box are 24 Marvel Super Heroes Jumpstart Boosters, each holding 20 Magic cards