Fear #20 wasn’t the first appearance of Morbius–but it was the first time he got his own comic, set squarely in the Marvel Universe.
He was originally a laboratory creation gone awry (because the Comics Code Authority barred vampire stories), but these stories seem to put him squarely into the vampire realm. But also the superhero realm! The blending of these genres made for a pretty cool book-and one scary looking antihero.
Issue #20 is mostly background, telling about his origin in Amazing Spider-Man #102, and his subsequent appearances up to his most recent one, where The X-Men took him in to examine him and try to cure him of his vampirism. But he quickly escapes so that he can run off and have his own adventures.
From there, Daemond, a Satanist cult leader, forces Morbius to do his bidding and kill the cultist’s enemies. Morbius does it (but he feels bad about it), until the cliffhanger reveals Morbius’ next target to be a little girl.
The cult is also linked to the Cat People who are later responsible for Tigra.
Morbius goes to their kingdom.
From here, we get Steve Gerber scripts.
Also note: Morbius shares these comics with reprints of old short stories from Marvel. Morbius’ stories are the only original material.