To help differentiate bone devils from being boring popcorn monsters with no special attacks or abilities, give them the ability to summon skeletons.

This should come with reasonable limits, such as setting their mspec_used field so that they can only do it every so often, and preventing them from doing it at all if there are a certain number of skeletons around them or on the whole level. Possibly limit it so that if they are not within the “misc item use” distance from the player, they will limit themselves to creating 0 or 1 skeletons.

Artifact tooled horn Horn of the Wild that summons a number of difficulty-appropriate tame animals to fight for you. (They might untame or despawn after a while.)

Allow more monsters to summon monsters friendly to them, but make them have to do a signaled multi-round behavior that can be interrupted by damaging them. E.g. printing a message that a monster is going into a summoning trance, or moving in a certain pattern.

A statue-like object which should be fairly destroyable (should probably be breakable by force bolts and maybe even attacking it with a weapon enough times) which provides a level-wide buff to certain monsters.

• An example of such an effect is “phylum gating” - e.g. if the statue-thing is an ant, it will grant all ants on the level a power to gate in more ants like demons do.
• This is the only example given, but there are plenty of other buff possibilities.
• The buff could also be within a specific area rather than level-wide.
• Rather than a new object, this could simply be implemented as a special flag on a regular statue.

An artifact magic marker that can be used normally, but also allows you to engrave the name of a monster species on the ground and make a monster of that species appear as a pet. This is subject to an invoke-style cooldown so it can’t be used rapidly in quick succession.

Add a “purple crayon” tool, which is used by engraving on the floor with it. If you engrave the name of a monster species, a single monster of that species is created, possibly ignoring reverse-genocide restrictions. This is a reference to the children’s book Harold and the Purple Crayon.

A Priest in good standing with their god and standing on or near a coaligned altar sometimes has the ability to use a special spell or prayer to call a coaligned Angel to fight with them as a pet.

Monsters pulled out of a bag of tricks are tame whether the bag is blessed or uncursed, and hostile only if it is cursed; however, all monsters created by it are temporary and disappear after several hundred turns.

Monsters summoned by an aligned caster (meaning a caster with a well-defined alignment: aligned priests, angelic minions) will also be minions of that god. Minions additionally get some extra benefits in exchange for directly serving a god, among which is periodically getting their HP topped up every now and again.

Make monster summoning less common, but make group spawns more common. (Not necessarily meaning group spawns caused by monster summoning.) In particular, when a monster that is a lord or prince to its kind spawns, it should always spawn in some associated retinue along with it.

Add a message for when create monster/create familiar/summon nasties fails to summon anything (may happen in extinctionist games).

New special room “lich hall”. Contains one difficulty-appropriate or somewhat-out-of-difficulty lich, generated asleep with difficulty-appropriate undead. One or two statues generate along the walls, and there are several spellbooks on the floor or in chests. Within the hall, the lich can summon more undead.

Distinguish between monster spells “summon random monsters” and “summon nasties”, allowing lower level casters to summon at-difficulty non-nasties.

Spell of summon single nasty: summons only one monster, but the game looks at the target’s current gear and defenses and analyzes exactly what sort of monster would be the best for facing it.

A magical whistle that instead of warping pets summons a temporary ally who disappears after a while.

Another type of magical horn, a “horn of heroes”, that when improvised on creates powerful allied monsters (dead heroes?). Ideally the summons would be temporary.

When werecreatures summon help, the help appears at random locations on the level, out of sight if possible, not around the player.

Add a “summoned” bitfield to struct monst, which is used to identify monsters that have been created through magical means. Should be a bitfield rather than a flag so that it can track different details of how it was summoned (from trap/wand/etc, by player or by something else; it probably doesn’t warrant a mextra struct). Summoned monsters can have various anti-farming nerfs applied to them: no training skills, no corpses, no deathdrops, no starting inventory, no experience, etc. Possibly, summoned monsters also disappear after a few hundred turns.