I have always liked the Role Aids line from Mayfair Games. With the exception of a few issues of White Dwarf magazine, for quite some time they were the only non-TSR publisher of material for Dungeons & Dragons I knew of (I hadn’t heard of Judges Guild yet). The content was compatible with AD&D, but different, in some good ways. The design methods were consistent with the times (i.e. fiddly and less consistent than we expect today), but the philosophy behind them led to game objects that felt specific and special.
The Archmagic box set was probably my favorite. The grimoires, spell books that were actually magic, were one of my biggest draws. The spells also… not so much that they were level ten, but that they deserved to be level ten, excited me. They were basically useless in combat because of the casting requirements, but their scope and grandeur made them feel special and unique.
For similar reasons, the Demons series is a close second. It starts with a breakdown of an infernal hierarchy, to give it all shape, and then describes a series of unique demons. It also set aside the idea of generic summoning spells, instead providing spells for summoning specific types of demons, similar to the invisible stolker spell.
I don’t plan to go quite as far as individual spells, but I do want to have distinct lists for each deity.
Heralds are a deity’s most powerful servants, probably in the CR 20-24 range (solars are CR 23, for reference), and each should be unique. A deity may have multiple heralds.
Heralds are all named, and not just named, but creatures with unique builds: possibly a base creature with class levels and/or templates. Initially I can get by with just some of the entity details (name, description, etc.); the full build can wait until I need it.
Summoning a herald probably requires a gate spell or similar ritual. As a direct servant of a deity it might not even be possible to summon a herald.
There are three grades of ally, suitable for lesser planar ally (6 HD), planar ally (12 HD), or greater planar ally (18 HD) spells. They probably have some customization, which might mean anything from minor cosmetic details to full reskinning. A deity will have multiple allies, and the allies might be specifically related to a herald.
While a deity will have many types of allies, they mostly going to be relatively consistent. At a start, at least, hound archons allied with Cestelline may differ from regular hound archons, but will be pretty similar to each other (same changes made). Over time, though, I expect I’ll introduce specific characters to the list of allies, and those named allies might show greater differences. For first cut, though, ‘lunar hound archon’ will be sufficient.
Summoning an ally is typically done using a planar ally spell. The same creatures are subject to planar binding, but that’s not nearly as friendly. Allies also overlap the summon monster spells, but the result is much more limited.
Summoned monsters are more or less generic, ignoring the changes common for the deity. That is, if you summon one of Cellestine’s hound archons you’ll get one that’s clearly hers (has the changes common to her servants), but not particularly distinguishable from each other.
These are all called using summon monster spells. They show up, act for the caster for a couple minutes, tops (one round per level), then disappear.
Summoning Multiple Creatures
Rules as written, summon monster and planar ally spells that bring multiple creatures bring groups of like creatures. Summon monster IV can bring one hound archon, summon monster V can bring 1-3 hound archons, and so on. Similarly, lesser planar ally can call one hound archon, planar ally can call two hound archons, etc. (which seems underpowered to me — what pair of 6 HD outsiders is going to be as effective as a single 12 HD outsider?)
For generic spells such as these, it makes sense to keep it simple. Since I’m going to the trouble of having distinct lists, though, I don’t see why a particular ‘summoning entry’ can’t be more varied. I can expect to have entries such as ‘fiendish warrior’, ‘hellhound’, and ‘fiendish warrior mounted on hellhound’… the sort of thing that is sadly lacking in the base summoning options.
As you might have noticed, I like frameworks that provide a consistent mechanism or guidelines for producing varied results. The entire Divine Trappings topic is about how to do that.
One aspect of this is having distinct summoning lists for each deity. While it makes some sense that allied deities might share lists, I’d like it much more if each deity had their own. (This incidentally extends to non-deities… I’d be happy to have a summoning list for the Infernal Court, summoning lists for the Seelie and Unseelie, and so on.)
Treating planar ally and planar binding spells more as templates than as generic spells also appeals to me. From a play perspective it makes sense they way the rules lay them out, because in an abstract way such spells probably should work much the same way, but I’d be quite happy to treat them as distinct, individual spells.
Or better yet, as rituals. I really like the idea of using the planar ally and planar binding spells as templates for rituals, with each ritual being unique. I’d probably then want to strike the spells from the spell list, so they’re only usable as rituals.
Which comes back around to Demons and Archmagic, both of which encourage this sort of thing. I would dearly love to have players looking for specific tomes and grimoires and whatnot, to learn the specific rituals needed to call the allies and other powerful beings they need to contact.