He invaded several kingdoms, including the Baldesian Kingdom, with the army of monsters, including Gilgamesh, and attempted to merge the two worlds at the same time
Certainly the Fiery is best in constructed, but somehow Wretched is the thing for cube
Omnath really loves lands, so team them up with anything that lets you play extra lands, plus other permanents with Landfall triggers, and its not hard to go-off, gaining an insurmountable value and mana advantage
Scryfall is perfect for finding exactly what you want, but you actually need to know what kind of card you want for it to work well
Secondly, we've also got access to some reanimation spells unique to UB