I would also hate to see Twisted Resurrection go, it's one of the more visually unique spells in the game. It could always be kept as a god ability, however. I'd also like to see Homunculus (
https://crawl.develz.org/wiki/doku.php?id=dcss:brainstorm:magic:spells:propose:homunculus) in the game at some point (but perhaps that could be an ability of some alchemy god).
The way I would see summoning in general being improved is introducing two caps - a per-spell summons limit, and a total summons limit. If you cast a spell that would take you over either limit then older/weaker summons will disappear to be replaced by the freshly summoned creatures. The per-spell limit can be quite low, which forces the player to diversify and use a few different summoning spells instead of just spamming the strongest thing they've got. Per-spell limits go up slightly with spell power, the total cap goes up with your Summoning skill - up to something like 16 at 27 Summoning. (Whatever the maximum limit, Yred/Beogh followers should allow you to surpass it)
Additionally, summons of all types should trickle down the stairs instead of arrive nine at a time. This will be a nerf since you can't have an instant 9-monster meat shield (maybe 2 or 3 max should arrive at the same time as you, and the number should also depend on terrain so you can't even guarantee surrounding yourself when you arrive in a corridor). However it will be a massive interface improvement whatever types of summons you're using.
Some ideas for Twisted Resurrection to make it less broken, even with a cap of say 3 abominations:
- Permanent allies could work something like perma-buffs - you have less MP the whole time you're keeping them alive
- Abominations slowly deteriorate. They are far more durable than most summons (e.g. you can expect them to last a whole level or two) but they don't last forever
- Abominations don't heal over time (and are easily damaged) - you have to keep supplying more parts from corpses to patch them up.