I'm looking for a sword and sorcery short story I read a long time ago: it's from the pulp era, possibly the 30s.
I used to think it had been written by Clark Ashton Smith as both the style and the atmosphere fit his works but after reading all of his stories I had to give up: now I'm clueless.
I don't remember much about the plot: only the antagonist, who's the plot's main feature too.
This man is a wizard, of the sword and sorcery kind: that is, a wizard who isn't shown casting fireballs or other spells over and over but is known to be dabbling with magic, hence very powerful, hence feared and respected.
He's quite old and probably evil too but always carries a backpack with a (sleeping) infant inside it.
Only in the finale it is revealed that the infant in the backpack is actually a parasite or symbiont that is controlling the wizard and devised this disguise to avoid being discovered.
Can you help me find the story and/or the author?