I think that Endowment represents transference. physically, this manifests as a control over the transfer of energy and matter between objects when the first object releases said energy or matter to the second object. cognitively, this would manifest as giving or endowment.
I also have a theory that Odium is Endowments opposite in a way. he also represents transference, but the other way around. instead of giving, odium steals. physically, this would manifest as a control over the transfer of energy and matter between objects when the second object "takes" said energy or matter from the first. cognitively, this would manifest as taking emotion.