Another neat trick most people overlook with Conjurer's Closet / Thassa, Deep-Dwelling is that the exiled creature returns under your control, not the owner's control
This imposing reptile could only be summoned after Orichalcos Shunoros was destroyed in battle, forcing the user to sacrifice 10,000 Life points
Alternatively, theres Teval, the Balanced Scale, which is more ramp-oriented and builds board presence via 2/2 creature tokens
It mostly revolved around getting Spell Counters on the field to perform actions
It's a card with high breaking power, but it's not stable, and I get the impression that it's a lower priority among power-up cards
For instance, a grave-counting creature like Wight of Precinct Six or Nighthowler would fit the idea of King growing with more guys in the yard, but they would also be disappointingly weak right now since you don't have a lot of mass self-mill at the moment (Stitcher's Supplier and Overlord of the Balemurk are the first things that comes to my mind)