Regalite

Regalite is a Regent-only relic that automatically gains 2 Block every time you generate a colorless card. In decks that generate colorless cards frequently, Block trickles in regularly, but 2 Block is an extremely modest number.

Even generating 3 colorless cards in one turn produces only 6 Block — less than a single defense card — which is virtually meaningless in high-difficulty fights. Even in a dedicated colorless build, other relics offer vastly more efficient defense.

Its only saving grace is that Block comes in automatically when you already have abundant colorless generation. Even then, Vitruvian Minion's cost reduction is overwhelmingly more useful, and there's almost no situation where picking Regalite first makes sense.