So is the manner in which Teferi, Time Raveler encourages all your opponents to play creatures that give their value up front with enters-the-battlefield effects and such, rather than playing the sort of good-on-rate creatures that Dungeon Geists can punish, such as Steel Leaf Champion
However, unike Donquixote Doflamingo, Rebecca is an ally of the Straw Hat Pirates, rather than an enemy
Anything that costs 6 or more automatically cascades, letting you chain spells for massive value
The lifelink helps to stabilize for any tempo you might lose through getting the hammer equipped and the trample ensures you will be able to take full effect of the stats boost
but I worry that a dedicated mill isnt going to pack the level of draw spells required to make it shine
Assuming that we'll have enough cards in the graveyard to make this interaction work, she can do something pretty interesting