The Verge lands, Unholy Annex // Ritual Chamber, and Unstoppable Slasher are all amazing, but Abhorrent Oculus is the one that spread its wings the furthest seeing success in Standard, Modern, and Legacy
We can equip one Energy card per turn
You can recast your spells with flashback, bring back your creatures with disturb and zombies nearly always make a second appearance thanks to decayed
Slap a couple of Powerful Energies on it to give it an attack boost and it can very easily take out most Pokemon with just one attack.
When Richard Garfield developed Magic in the early 1990s, there was no precedent for balance
Tiamat If this D&D legend resolves, you can be sure you're never running out of gas for the rest of the game