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.
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.
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.
Gulthias trees should have an attack that starts a timer where you gradually turn into a blight, which ends the game if you succumb to it (without life saving, at least) since you have been converted, similar to how turning to slime works. Also similar to sliming, if you become a blight, you should be one in any bones file that gets created.
A damage type that shuffles around the player’s intrinsics, never taking any away for a net loss, but always rearranging them, so you could lose fire resistance but gain teleport control, or lose telepathy in exchange for intrinsic protection from shape changers.
Special damage type AD_GNAT: when hit with it, you are compelled to attack the offending monster on your next turn if able. (Or as a weaker version, you can do things other than attack, but if you want to attack you must attack the offending monster).
Not specified what would happen if you are hit by two gnat attacks on the same turn.
Disfiguring poison that drains Charisma.
Add the “necrotic” damage type from D&D, so that evil monsters can deal corruptive or decaylike damage without resorting to instadeath, level drain, or disintegration.
Add a new damage type AD_CHOK, for specific suffocation attacks (so that rope golems’ AT_HUGS AD_PHYS combination doesn’t have to be interpreted as choking).
Vampires drain levels much less than they currently do, or not at all; instead they use a bite with an AD_DRHP damage type (described in #1627). Possibly give vampires one AD_DRHP attack but let vampire lords keep one AD_DRHP and one AD_DRLI.
Monster or damage type that un-erosionproofs gear, not very common.
Mosquitoes, an a-class monster which uses an AD_DRHP attack, which replenishes the mosquito’s health by some fraction of the damage it dealt you.
