Teferi, Time Raveler, and the especially spiteful Ashiok, Dream Render
As the original Mewtwo EX was released in 2012s Next Destinies expansion, both it and the Celebrations reprint are legal to play in the current expanded format
If it doesnt, it floats
For example, there are cards that, despite being heavily skewed toward defensive use, contribute significantly to win rates due to their high power level, making them well worth including even in aggressive decks (a prime example being Force of Negation, a counterspell that is difficult to use aggressively)
The remainder of the list looks to generate extra wraiths the Nazgl can pump up, and theres plenty of card draw and protection to keep the wheels turning and your legion of monstrosities expanding
Seems ok in limited, in other play you're better off preventing the creature from resolving in the first place