Moldessa is a card good for mid to early game for destroying monsters with low hp. When placed, it will do 2-4 damage to a random enemy monster. If no enemy monsters are present it will do no damage. When Moldessa dies, it will add a random other Mold to your hand.
Because Moldessa is a Mold, Moldbygg is able to increase its HP. But because Moldessa's HP is so low to begin with and has a Dust effect, this isn't worth it that much.
Beta 21.1 gave it an updated image.