Emerald Lorcana cards tend to prioritise defence and effects over strength, which you could choose to balance by combining it with a more challenge-focused colour such as ruby or support with the protective powers of amber or amethyst
Its not an adventure spell, but Uro is fantastic when your strategy is self-mill
Historically, the play rate (how much of the metagame share a deck has) of those decks has been low enough that it hasn't been an issue
Making 1/1 lifelinkers is a reasonable trade for the lower starting loyalty as you grow your life total and Sorins loyalty simultaneously, even if all you are doing is chump blocking every turn
By the way, BGU mana cost is also quite fitting (at least for me), possibly representing Sin's connections to oceans (blue), death (black), and the natural cycle it's strangely bound to (green)
VENERATED ROTPRIEST Venerated Rotpriest is perhaps the most powerful Toxic creature printed for its ability to threaten wins out of nowhere across multiple formats