Board Thread:Legitimate Canon Questions/@comment-75.118.201.227-20140402210414/@comment-4091815-20140402213058

Lydia was acting on the memories Peter implanted in her through the bite.

He needed someone alive to bring Derek together with his body at the right time on the full moon and he claims he "knew" Lydia would't die or be changed by the bite so he used her.

He was merely his hands since he was dead and couldn't lift anything himself.