aranea could transform between the appearance of a humanoid and a giant monstrous spider.[1] Their humanoid form was that of a Calishite human, a Calishite half-elf, or, in some rare cases, a drow.[6] The form and gender they could take was fixed at birth.[3]
In their natural form, these creatures appeared to be giant humpbacked spiders with some subtle differences. In this form they also had a pair of short arms ending in many-jointed fingers and double-jointed thumbs, which extended from below their mandibles. Oddly, their brain was not located in their head segment but in a large hump on their back.[1]
Aranea also could take on a third, hybrid form.[3][1] This form was humanoid, but the aranea bore sharp fangs,[3][1] had spinnerets[1] in his or her hands,[3] and had four eyes instead of two.[3] On occasion, the hybrid form would also include additional arms, but never more than 8 in total