phoenix cards mtg Heart you may pay Phoenix, 40 cards | Magic:

Marchesa, the Black Rose : When I build Marchesa decks, I use plenty of creatures that naturally enter the battlefield with +1/+1 counters, which means that, with Marchesa, the Black Rose on the battlefield, we can feed one to emerge without going down a card

Late-game, when everyone is looking to close out the game, then it seems fine

Again, it depends on your environment how deep you go with sideboard cards

In Cube, there has been some talk about this card and some lists are trying it out

One possibility is to cast Apocalypse, a card that gets rid of everything, including your hand, leaving you only with Barren Glory, but that needs to be done on your upkeep, so there are options like Leyline of Anticipation or Emergence Zone to give these spells flash

On paper, it seems pretty balanced and self-restricting, for sure there won't be any oppressive card with this ability