Based on casual play alone, Ob Nixilis is probably a $2 card, so the premium here tells me that some people believe that Ob might see play in Standard or Modern as well
We decided to play Compulsory in the side (I say "we" because I built the deck with my teammate Diellor, who told me that compulsory could be a nice tech)
The combination of universal Fire Energy support, high base HP, and late-game nuking potential makes Mega Charizard X ex a central threat in Fire archetypes but now, this card also looks like it belongs on a first place medal as well as a binder
Other takes on this strategy have centered on Brain in a Jar, which has the disadvantage that it can be slow to get going late, but its advantage, in addition to not being an enchantment, is that it has an interesting combination with Days Undoing that allows you to cast Days Undoing on your opponents turn, skipping the end the turn clause, which means that the Days Undoing ends up in your graveyard
These are Kirikio's Pokmon TCG debut, so we will have to keep track to see how their role in the hobby progresses