Shimmering dragons’ breath attack should be a “tractor beam” sort of thing, which pulls you towards the dragon most of the time, but occasionally pushes you back. This can pull or push you over dangerous terrain.

Chupacabra, a canine-class monster that is vampiric, with some sort of draining bite. In a reference to how some real-life sightings of it have turned out to be mangy canids, it may appear at first as a coyote.

Wendigo, a high-level Z-class monster which normally hits using cold damage, but if the target is resistant to cold damage, it instead hits with Famine’s hunger-inducing damage type. If you commit cannibalism, you may polymorph into one (permanently?) as a side effect.

Memril, a fantastic insect (so in the x class rather than the a class) which has two bite attacks, each with a chance to decapitate the target. It never generates randomly until the Wizard of Yendor starts harassing the player. It may be a valid target for summon nasties.

Firefly, an insect which emits light and has at least one attack that deals fire damage.

Executioner beetle: an insect whose bite has a chance of decapitating its target.

Vorpal bunny, a magenta r monster with a deadly bite: it decapitates you if your HP is at 50% or less, and bisects you otherwise. Probably a reference to the killer rabbit from Monty Python and the Holy Grail.

It should probably only generate in Gehennom, or be unique and generate in a specific area or off-branch of Gehennom, or be psuedo-unique by giving it a birth limit of 1.

Glowworms, a w monster that emits light in a radius of 1. Maybe they have a blinding bite attack, but that may be taking the light theme a bit too far. It may also devour globs.