RogueForge is a roguelike deck-builder where an LLM forges every card, enemy, event and hero during the run. The model never touches game logic; it picks from whitelisted effects, and this validator decides whether the result is fair before a player sees it. It is the real thing, ported line for line from the Python backend.

A card's power is a weighted sum of its effects. The acceptable band for each (rarity, cost) bucket comes from the real Slay the Spire Ironclad cards in that bucket, so "balanced" is defined by data, not by taste. In band: accepted. Slightly out: clamped one point at a time and the rules text re-rendered. Far out, or structurally wrong: rejected, with the reason sent back to the model.

Try 40 damage on a 1-cost card, poison on an Attack, or a Rare that gains 2 Block.