This is the kind of deck where an artifact that will copy your Harnfel, Horn of Abundance might make sense, though Red does also have ways to make token copies of creatures
Previously, in cases where a card's mana value differed from the resulting spell, such as with some modal double-faced cards or cards with an Adventure, you could cast a spell with a higher mana value than the exiled card.
There are some arguments against a strategy like that, especially because it relies on your opponents creatures more than your own
Blight Titan The fifth card is Blight Titan, a 4 Black Black cost creature with a 6/6 body and deathtouch that makes me wonder about the titan cycle from earlier core sets
Once per turn, you may detach one XYZ material from Adreus to target one face-up card your opponent controls and destroy it
I think both games use skills that translate fairly well between them