I wrote a deck about him over here
The five decks included Izzet spells matters, Simic +1/+1 counters, Golgari reanimation, an off-putting Boros aggro-midrange deck that was wildly inconsistent, and Orzhov enchantments
This dilemma is not that much different than what happened to the music industry in the late 90s or the film and TV industry right now
Aggressive decks get a lot out of a 3/1 with flash, various flavors of aristocrats love a cheap creature that sacrifices itself, and any deck can use a 2-drop that stays relevant throughout a game
Speaking of card draw, Eye of Vecna seems like a colorless Phyrexian Arena in this deck, and we shouldnt have any issue paying for its trigger since the decks average mana value is under three
Dungeons can be accessed when a card has the phrase Venture into the dungeon on it, and has you journeying through different iconic D&D dungeons: Tomb of Annihilation, Dungeon of the Mad Mage and the Lost Mine of Phandelver