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.

If you would get no benefit from using Elbereth because you are a vampire or otherwise evil, you should be prevented from engraving it.

There should be a cooldown on using Elbereth to discourage overusing it in situations where you’re in over your head. For example, after successfully engraving it, all attempts to engrave another for the next 30-50ish turns will fail, possibly even if it gets smudged.

Reading a scroll of scare monster teaches you about Elbereth.

Getting amnesia can strip your knowledge of (and therefore ability to write) Elbereth.

Remove the Elbereth from the floor in Sokoban, since this means that anyone who finishes Sokoban automatically gains knowledge of Elbereth. Instead, place a burnt Elbereth somewhere random on the 9th to 14th levels of the dungeon.

Elbereth only protects you when the game considers you a beginner.

Aggravate monster, as well as possibly wielding Stormbringer, disables Elbereth’s protection.

Procedurally generate the game-equivalent of Elbereth each game (the literal string “Elbereth” does nothing special anymore), and make it fairly likely to appear somewhere in the Dungeons of Doom.

If you attack a monster while standing on Elbereth, all monsters in line of sight stop respecting Elbereth.

Conflict negates Elbereth protections.

Having an Elbereth square fade under you in 3.6.1+ makes the square permanently unengravable.

You should be prompted to confirm before attacking a monster while standing on Elbereth.

Hostile elves can engrave Elbereth and use it on the player, scaring them.

Make Elbereth work the same as it did in 3.4.3 for animals or mindless creatures. Intelligent foes won’t be scared by it, but they merely won’t attack in melee.

Elbereth should work from the very outset of the game, but get less effective over time.

Elbereth should not work until the hero discovers it in-game. (Similar to dNetHack’s wards.)

The list of monsters that ignore Elbereth should be increased, but the list of monsters that ignore scare monster should remain the same or decrease (3.6.0 Quest nemeses excepted). Perhaps scare monster should be renamed to “scare creature”, as it scares humans and elves, which are not really monsters.