Sondok might be able to meld a lock from the stone, but she's not a maker of things-- it would require time, concentration, and probably a few tries, and good luck convincing her to stop protecting her precious thing when there's a hostile murder engine in the same room.  Chorgath himself stands a much better chance of telekinetically carving/improvising something that would work to elicit the Key's effect-- if he wants to carve something in the stone door, it'd be a Miscellaneous action Speed 5 DV -1, difficulty one with a cumulative difficulty of 10.  There has to be a certain minimum of moving parts for the key to interact with-- it won't be pretty, but it'll do the job.  If you want to change your action to do that instead, that's legit.