Variants of a mold are catalogued separately, so each one has its own sets and minifigs. Check these too if something you expect is missing here.

• 33721c01 Wings, with Black Rock Limbs and Dark Purple/Light Blue Membranes Print, (Colossus) [Complete Sheet] this part is a sub-part of it
• 33721b Wing, with Black Rock Limbs and Dark Purple/Light Blue Membranes Print (Colossus) this part is a pair of it