Clunknad Spanner is the alleged skeleton wizard mentioned by Emperor Tengu as a part of a joke. The emperor also gives the player a Mystery Sack in order to identify themselves to the wizard that should help the player to kill the notorious Grievewrath.
The dialogue with Tengu is satire, mocking traditional RPG quest structure and the use of magic. Both of these NPCs are not present in Kenshi. The Mystery Sack is, however, very real.