Twinmold consists of two giant, worm-like creatures in a desert arena. For the blue Twinmold, use the Giant's Mask to become Giant Link and punch or throw it. For the red Twinmold, you'll need to use your sword to attack its head or tail, or use Light Arrows to stun it. Focus on one at a time. The Giant's Mask is highly recommended for this fight, as it trivializes the blue Twinmold and makes the red one much easier. Be wary of the quicksand and their charge attacks.
