I have mentioned this in another post, but again, I didn't make it clear how to get this monster. Here is the process:
1) Raise a Henger to Class B with 600 or higher Int.
2) Bring your Henger to Malkt.
3) Bring you henger to the large monolith with the figure of a double life-size human. You probably found this monolith when you were looking for Henger parts.
4) Your Henger will enable you to read the writing on the monolith which has the tablet "MECCOLD".
5) Leave the ruins by going back to camp.
6) Use the Tablet "MECCOLD" at the Shrine to regenerate a Franken (Henger/SP-U).
It's easy. Any henger that can get to Malkt will be able to unlock the Franken.