also! re: the old asks on immortality and supernatural races (that I mentioned in the tags of vilna's post yesterday), these are (I think!) all of the most relevant ones in my spreadsheet under 'supernatural races':
ghosts vs. spirits, generally
ghosts vs. spirits and the Echo World
what races can humans be turned into?
hybrids (and specifically their strength vs. non-hybrid supernaturals): Pt. 1, Pt. 2
formation of hybrids (likelihood, occurrence rate in human world vs. Echo World): Pt. 1, Pt. 2, Pt. 3
supernatural lifespans: not all are truly immortal; healing accounts for a lot of functional immortality (pt. 1, pt. 2); some (not all) races (e.g., vampires) will not die unless killed
supernatural races have differing rates of healing speed
witches: human-born witches exist (and are considered human); some have familiars, depending on type of magic practiced; witches can be turned or natural (as well as human-born)
(also tagging @carriehobbs because you mentioned wanting links to these asks! <3)