Warp Beast Generator
So, I freaking love that the creature that has since evolved into modern D&D's iconic (yet mechanically about as interesting as a bowl of plain, room-temperature porridge) Displacer Beast started out in B/X as the Warp Beast.
Visually, it still hits the same beats - a big, six-legged panther with prehensile, Little Shop of Horrors tentacles protruding from its back. Mechanically, little has changed either.
This is a shame, because while I can sort of accept the modern displacer beast as a kind of weird invasive jungle-dwelling species (maybe akin to the Forgotten Realms' version of Pablo Escobar's hippos), the idea that a massive nightmare cat that crawled out of the howling nothingness at the edge of reality is basically just a lion with a paralysis attack is disappointing.
Building on another idea I've heard echoed a lot throughout the community - that the entry for Orc in the Monster Manual represents "an Orc" not "the Orc" in some platonic and bioessentialist vein - I've been playing around in my own games with the process of creating greater variety among monsters. Sure, the B/X entry is for "a Warp Beast", but what's "this Warp Beast" like?
Add to this my opinion that, the further away we get from the core of medieval Eurocentric "normalcy" that dogs a lot of how we think about D&D, things become less predictable, less consistent, and less effectively codified, and you get this: A Warp Beast Generator.
If the nightmarish reaches of the far eldritch warp exist, then I want nightmarish and eldritch Warp Beasts to come crawling out of it. Admittedly, old school dnd art - not to mention the Warp Beast that Kyle Latino drew for OSE - nails this way, way, way better than 5e.
"Warp Beast" Old-School Essentials: Classic Fantasy Monsters - Kyle Latino, Artstation
This, I love. It makes me wonder what other godawful nightmares might be lurking out there beyond the stars and the darkness at the edges of our vision.
This generator is hugely inspired by the Twilight Vermin in Vasili Kaliman's excellent module Night Land.
Use these stats as a base and build from there.
Armour Class 4 
Hit Dice 8** (32 hp)
Attacks1 × d8 (or using abilities)
THAC0 16 [+3]
Movement 120’ (40’)
Saving Throws D10 W11 P12 B13 S14 (6)
Treasure Type None
Special. Roll. It is…
Table One (Form, d6)
Table Two (Description, d10)
Shaggy Fur; the stink of animal musk
Strange Markings; camouflage for the wrong climate
Glittering Scales; jewels across its back
Lurid Feathers; plumes and crests like heraldry
Writhing Tentacles; grasping, reaching
Craggy Hide; harder than stone
Ashen; pale, lifeless
Formless; shifting, changing
Visceral; guts and gore; the inside on the outside
Chimeric; many are one (roll again on Tables 1, 2, and 3 and combine)
Table Three (Description, d10)
Translucent (surprises on 4-in-6; -2 to hit it with ranged weapons)
Horned (d10 Gore Attack)
Winged 180’ (60’) flying speed
d4 x 2 Extra limbs (1 extra attack for each pair)
Venomous (save vs Death on a critical hit)
Chitinous (AC 1 )
Gelatinous (absorbs on a hit, restrains for d6 additional automatic damage per round)
Necrotic (permanently drains 1HD on a hit)
Many-Eyed (never surprised)
Humanoid (intelligent, dextrous)
Table Four (Abilities, d10)