Red Planet

The Red Planet is the true form of The Tall Man, accessible only through the Dimensional Fork. It's where The Tall Man's avatars dispatches his slave Lurkers in barrels for unknown duties. The Red Planet is notable for its high gravity and peculiar atmosphere that requires a gas mask to breathe safely.

Phantasm
The Red Planet makes its first appearance when Mike, Reggie and Jody discover the white room in the Morningside mausoleum. In the room are stacked barrels and a Dimensional Fork that Mike touches, discovering its purposes.

Experimenting with the Fork, Mike accidentally pushes his hand in too far, and gets sucked in. He falls from a great height (suggesting the corresponding Fork is on a cliff), only to be caught and pulled back by Jody. Briefly, we see the Lurkers unpacking the previously sent barrels on a rocky terrain stretching to the horizon. After returning, Mike theorizes that the Tall Man shrinks his victims down into Lurkers to cope with the Red Planet's gravity.

Phantasm II
Mike opens a sealed compartment in the Perigord mausoleum, where he, Reggie and Liz discover another white room with the stacked barrels and Dimensional Fork. Shortly before Reggie can set fire to the place, they are attacked by the Tall Man, who grabs Mike and Liz, and tosses the former through the Fork. Reggie, trying to help, is pulled through as well.

The two find themselves lying on the rocks, in the same area seen in the first film, although now the Fork is actually on the ground. Fighting against the gravity, Mike climbs over Reggie(whose feet are still hooked on one of the poles) and back out through the Fork, pulling the latter out as well right before an awakening Lurker could reach him.

Phantasm V: Ravager
In order to confront The Tall Man, Mike leads Reggie to a Dimensional Fork in one of his occupied buildings, and offers him a gas mask. The two storm through and quickly find The Tall Man holding Dawn prisoner over a canyon.

Mike attempts to unsuccessfully negotiate, but The Tall Man merely points out the foolishness of his loyalty and how he and Reggie are merely his playthings. He then sends a gold sphere towards Mike, but the latter is able to redirect it, angering the Tall Man, who orders his Graver to snap Dawn's neck much to Mike and Reggie's horror.

Chunk reveals himself to be in disguise as one of the Lurkers, and uses a set of grenades attached to his body to detonate the Tall Man, forcing Mike and Reggie to escape back through the Dimensional Fork. A badly injured Chunk himself somehow manages to find his way out of another Fork later.

Appearances

 * Phantasm (1979)
 * Phantasm II (1988)
 * Phantasm IV: Oblivion (1998) - Archive footage
 * Phantasm V: Ravager (2016)