The Following Thing: Init +2; Atk bite +4 melee (1d3 plus DC 13 paralyzing venom); AC 15; HD 3d8+10; hp 30; MV 30’ or climb 30’; Act 1d20; SP venom, pursue, impossible to kill, one night only; SV Fort +4, Ref +4, Will +18; AL C.
It looks like a well-dressed man in a long black suit with tails, but its face is a stag skull with dead white eyes. It does not walk, but crawls on all surfaces with equal ease. Once it selects a victim, it will pursue that victim relentlessly, attempting to paralyze it with its venomous bite (Fort DC 13 or paralyzed 1d3 rounds) in order to remove and eat its victim’s eyes. It can remove and devour one eye each round from a helpless victim.
Once a victim is selected, the Following Thing can always follow it, appearing 1d6 x 10’ away in a random direction each time an insurmountable barrier is placed between it and its prey. (The judge may wait to have the Following Thing appear so as to build up tension.) If successfully Turned or slain, its body fades away with a high-pitched giggling noise, and it is forced to wait 3d6 turns (30 to 180 minutes) to reform and pursue. It is impossible to kill.
The Following Thing is only active against its selected victim for one night; once dawn arrives the victim is no longer followed. How it chooses its victims is unknown, but some have speculated that miscast spells or the gods’ great disapproval might draw it. In some tales, the Following Thing appears as a punishment, sent by forsworn patrons. Few people are ever selected by the Following Thing more than once, and the Wise believe that there is only one such monster in all the multiverse.
(The wise may, of course, be wrong.)
Throw this monster into your Halloween adventure!