HeavyMetaldramon was introduced in the Digimon Liberator webcomic, and it quickly became a fan-favorite, alongside its Tamer, Yuuki
While thats fun and neat, it can also OTK when going second, thanks to Borrelsword Dragon
This is because you can select cards in your Graveyard that can return to the Extra Deck (for example, Synchro Monsters), so there is no guarantee on at least 2 cards being returned to your Deck at the end when Pot of Avarice's second effect (drawing 2 cards) resolves
Gaea's Blessing : Whenever a spell you play is countered, draw a card
But the biggest benefit probably comes from the Urzatron ( Urza's Mine , Urza's Power Plant , and Urza's Tower ) as well as Cloudpost , which produce more mana when they see more of their associated land types