A LoRA for clothes with tentacles lining them / living clothes, trained on a wide selection of images from multiple artists & groups, primarily: Touchable, とりさん (Torisan/tori33), 九反 (kutan/ktn_kuta), イカめし, 黒鎧 (akfall_bonde), and a bunch of one-off or single series of images from other aritsts. This should hopefully give it less impact on style and more flexibility in concepts than some of the others out there. Also I didn't notice there were any others for Illustrious until after I trained this, somehow.
Main trigger is "tentacle clothes", but adding "tentacle [article of clothing]" seems to work, based on my initial testing. "Living clothes", the Danbooru tag that covers this and some other concepts, also helps.