Several potential additions for the clerical spell school:

• Bless: this could either be a low-level spell that works like it does in D&D where it gives you a to-hit and damage bonus, or it could be a high-level spell that blesses an item. Possibly it could bless items when cast at Skilled or above.
• Sanctuary: a medium-level spell that effectively makes monsters treat the 3x3 area around you like a coaligned temple for a limited time, unless you take a hostile action which ends the spell.
• Command: Drop: forces a monster to drop its weapon.
• Inflict Wounds: medium-level spell that deals damage while being in the clerical school. Damage should probably scale with skill.
• Hold Person: paralyzes a monster (or more strictly, a humanoid); fits right in since enemy priests can already cast this.
• Silence: Temporarily stops a monster from reading a scroll or casting a spell. Not specified if this should be a debuff or create a region of silence.
• Dispel Magic: Removes magical effects from a monster or multiple monsters. May be of limited use unless added to a variant where monster magic buffs are significant.
• Freedom of Movement: Grants temporary intrinsic free action, allowing you to free up a ring slot.

It should be possible to define anti-spawn regions in a level, like how monsters will not generate in the Sokoban hole corridors but more general. It should still be possible for monsters to appear in specific places within such regions that are specified in the level definition, but monsters specified to appear in random places won’t, nor will any monster that generates after the level is created. This could be done by checking the anti-spawn regions in the makemon_rnd_goodpos function.

Implement antimagic fields as a region. They are a static, possibly invisible region inside which magical effects cannot function, including all of the following effects:

• Completely disables spellcasting both for the player and for monsters.
• Monsters behave as if cancelled, as do you if you are polymorphed.
• Enchantments do not add to AC or weapon to-hit or damage.
• Magical extrinsics are suppressed.
• Potions have no magic effects (so non-magic potions like acid work the same, but e.g. drinking a potion of object detection would consume the potion and do nothing else).
• Scrolls do nothing; they won’t disintegrate when read but won’t do anything else either. “You pronounce the formula, but nothing happens.”
• Wands do nothing; they won’t consume a charge when zapped or engraved with, and can only engrave in the dust.
• Artifacts have no special powers.

The anti-magic field trap could be repurposed into casting one of these rather than draining energy, which could be split off into a different trap type.

Region of reverse gravity: while inside the region you gain levitation if you don’t have it, or lose levitation if you do have it. This means if you want to pick something up off the floor, you would quaff a potion of levitation. If implemented as a separate effect on top of levitation, you might have no control over your movements, as you do on the Plane of Air - magical sources of levitation give you control over your movements there, but in order to be levitating in a reversed-gravity area you cannot have any levitation magic.

Not specified what effect would create the region.

If you overenchant Stormbringer and it vaporizes, it should turn into an actual storm: a region of clouds that shoots paralyzing lightning, the same way as the storms on the Plane of Air work.

New clerical monster spell (possibly also a player spell) that creates a region of black storm clouds between the caster and target and moves across the map towards the target. The clouds block vision, can strike anything in or near them with lightning (though not intelligently), wet items on the floor beneath them and in the inventories of monsters beneath them, hit things with gusts of wind if those are implemented, and can spawn temporary lightning monsters that vanish when the cloud does.

Another variant of this idea is as a static cloud that can be targeted like a stinking cloud, probably as a level 7 spell (depending on how bad the lightning is).

Split up the job of TELEPORT_REGIONs in special level definition files into it and NOENTRY_REGION. Now, TELEPORT_REGION defines a region that cannot be horizontally teleported into or out of, whereas NOENTRY_REGION defines a region where you cannot enter the level if arriving in an unusual way (level teleport, falling in from above, cursed potion of gain level).

In wizard mode, attempting to teleport into inaccessible terrain or into or out of a teleport region should prompt the player to confirm the teleport. If they confirm, they override any restrictions; if not, it prints “Sorry…” and works like normal.

Assuming the game supports creating temporary regions of non-poisonous gas clouds: New “smoke bomb” potion. It makes you choke/vomit when quaffed. Intended to be thrown; where it shatters, most of the surrounding terrain will be transformed into cloud.

Vanilla has since added non-poisonous gas clouds (for things such as mist from zapping fire over water), and this effect could work just as well by breaking a smoky potion, instead of adding a new object.

Add some region code preventing monsters from generating in (or even better, moving into) the pit corridors in Sokoban until the level is solved.