When comparing local forms of world religions--the idea that a local religion can be created by combining and incorporating other religions together, or layering one on top of another is known as

Syncretism.

Explanation:

When comparing local forms of world religions--the idea that a local religion can be created by combining and incorporating other religions together, or layering one on top of another is known as syncretism. Syncretism in anthropology is defined as the blending of different religions seeking an underlying unity in what seems to be diverse.