Its got the right mixture of powerful Creatures and spells with just enough utility and removal to win games
Interestingly, one Domain Overlords list ran both Starting Town and Ultima, illustrating how different support tools from the set can converge in a single build
They both also synergize nicely with Miirym, Sentinel Wyrm and Reflections of Littjara (which is already included in the deck), as you'll get activations off both your original creature and their clone
There was definitely a period of time where I noticed my play patterns with the card were actively sabotaging my land drops later in the game, and during the early days of Commander, where big, splashy spells were king, I wrote Land Tax off as being more trouble than it was worth
Whoever wins that mini-match gets to tutor up any two cards they like from their deck a pretty powerful reward for the hassle