suggestion for a couple of creatures for the bestiary:
intestinal caecilia: a extremely long, tentacle-like creature with a large mouth that causes extreme swelling and sensitivity to the victim's anus rough specific enzymes secreted from it's salva, before forcing itself inside. name comes from its full lenght is nearly the same of a anthro's intestine.

black seeder: the female of a lesser eldritch creature that rarely attacks weaker or defeated adventurers with female genitalia that traveled too far into the darkest corner of a dungeon. after approaching a defeated adventurer, they begin to probe them with its ovipositor, first injecting a concotion that nakes the victim stretchier, then the empty egg's chorion and finally the egg itself. after it's done, it drags the victim, now with the appearance of a exaggerately pregnant person, to a much safer place for them to be rescued by others. since the egg is too large to be manually removed, the only safe solution is to fertilize it, which will cause it to hatch and drammaticaly shrink in size after less than a day

Hmmm, both critters sound fun! #1 seems kinda like a butt-leech!

i know, but it's kinda cliche to have leeches, caecilias are commonly known as penis sakes, and it sounded much funnier.
the chorion thing is inspired by wasps that lay their eggs inside trees, which have a very long and thin ovipositor