Sephiroth, Renowned Soldier Lord Conrad, the Strict Al Bhed Salvager Creatures that assist in draining the opponent's life
Bosh, Iron Golem Bosh, Iron Golem has a pretty attractive textbox, but that mana cost is hard to stomach in the 2020s
Nadu, Winged Wisdom created similarly unfun and unskippable gameplay loops in Modern and dominated the meta and tournament structure, but it remained legal until the next scheduled Banned and Restricted announcement
It's not exactly a mystery anymore, even if it was originally meant to be, and if you're curious to check it out for yourself, you can do so here: That's one Unsolved Magic Mystery now officially put to rest, even if the circumstances might be a bit disappointing
Invasion of Amonkhet // Lazotep Convert seems to be quite usable on its own at least, synergizing very well with the front facing ETB effect no matter which graveyard you choose
The available cards include Aragorn, a hero card that doesnt count towards a players hero limit and can support other hero cards but can spell the end of the game if he is ever defeated