How many spiders can a player character have through class features, spells, etc?

I’ve been considering making a character who is obsessed with spiders! I want to know how many spiders a player character can have at any one time through spells, class features, etc. (so not by collecting or befriending or taming existing spiders, since that could be infinite spiders given enough time).

Assume that the character is level 20, and that they have whatever ability scores are necessary for multiclassing, etc.

I will place the following allowances and restrictions on this build:

  • Becoming a spider, whether via Wild Shape or polymorph, counts as one spider;
  • For the purposes of something like find steed, since it says "(Your GM might allow other animals to be summoned as steeds.)", we can assume that the DM is up for this and that a Giant Spider is on the table as a possible mount;
  • Hence the spiders don’t need to be "Beast" type creatures, summoned spirits in the shape of spiders count;
  • That said, as above, the spiders must come from class features, spells, magic items, etc, so no gathering existing spiders, even via charm beast, dominate monsters, etc.
  • No help from friends (unless they are being polymorphed into spiders by you);
  • Feats and Epic Boons are allowed, but no Unearthed Arcana for this one (largely because of the Swarmkeeper ranger, because swarms get complicated; I’m less strict about other UA though…)
  • Magic items are allowed, but I’m excluding spell scrolls, since otherwise we can essentially have infinite castings of mass polymorph or whatever;
  • Since it came up in comments, for the purposes of pixies summoned via conjure woodland beings casting polymorph, according to this Q&A, they can keep concentration after being dismissed, but probably won’t, so I’m ruling that pixies will stop concentrating after being dismissed;
  • No "rinse and repeat" solution for infinite spiders like casting true polymorph each day;
  • Hence this must be something that should be achievable within one day (so you start the day with 0 spiders; how many do you have by the end of the day?);