竜姫の咎 (Ryuuki no Toga, "The Sin of the Dragon Princess") is a push-your luck engine building game. There are only five days left before the final battle - can you defeat the enemy and become a legendary hero?
Long ago the Dragon Princess broke a taboo and had a child with a human. The "Sin" was a target for all the monsters in the world, and to defend her child the Dragon Princes descended into the Abyss. After an unimaginably long time, the Abyss transformed the Dragon Princess into a monster, and she's coming to reclaim her child and destroy the world in the bargain. You have just five days to defeat her.
Each round has three phases: card acquisition, playing units, and deciding whether to challenge the monster. A number of cards equal to the numbers of players is dealt face-up, and everyone reveals which one they want at the same time. If there are any conflicts, the start player for the round decides how to resolve that, and it doesn't have to be fair. Next you play units that add to your battle strength. Some units can be played for free, but advanced units will require spending mana of right color from weaker units. Finally you decide if you're ready to challenge the monster. You only get to do this once, so you want to wait until you're strong enough, but not so long someone else beats the monster first.
—user summary