From publisher blurb:
Essential Enemies 4: Between Two Worlds is a third party monster manual for use with Old-School Essentials and other old school fantasy role-playing games.
This zine contains the following monsters:
The Abnormality: A many-limbed, multi-headed angel of destruction that comes to destroy a city once every thousand years.
The Amalgam: A bizarre creature that is the combination of dozens of people. Now it tears holes in the walls of reality, opening portals to the strange new worlds beyond.
Bugbears: Insect-faced beings from another world, who hide shiny treasures underneath their fur.
Echo Tourists: Slug-like aliens who come to a tower in the middle of the desert to ride their flying carpets.
The Frost Giant: With the help of his frost gones, this villain seeks to destroy the heat of the universe. He comes with a dungeon!
The Griffarcus: A serpent-tailed beast of burden that can move between worlds, potentially taking a rider with it.
The Howling Helm: A magic helmet that summons ghosts to fight for the one who wears it. But other monsters in this book would prefer it in their possessions, as opposed to yours.
Living Psychopomp: Beneath the unholy mountain lies the well of souls. This being is not dead, but acts instead as a curator and guardian.
Mouth Eyes: A thing with mouths in its eyes that likes to abduct people and subject them to the magic of distant planes of existence to see how their minds and bodies change. If you survive such abduction, you may return mutated beyond recognition!
Slugbears: They come to our world from a distant star, and while nobles have found some of them to be docile servants, some go feral and flee into the wilderness.
Spirit Trader: Though its appearance may seem odd, this creature is an interdimensional merchant who buys and sells all kinds of spirits.