I thought this was the debut of Scarecrow until I researched it a little and saw he’d already appeared in Dead of Night #11. Still, he’s an interesting concept: He’s a literal scarecrow, except instead of being placed out in a field to ward off crows, he’s drawn in a portrait, where he wards off a demon invader.
As far as I know, this is Ruben Yandoc’s only Marvel book. He lived in The Philippines, and drew a bunch of 1970s DC books like Sgt. Rock, Weird War Tales, The Unexpected, and House of Mystery.