Ancient ghosts, truesight ability

what about introducing ghosts in ancient ruins? maybe the ancient civilization simply died after opening the portal and now their souls haunt the ruins. they can't be seen normally, but you can hear them and they activate sculk sensors with their moans, so you can guess where they are.
you can see them with special lenses to wear on your head or hold in your hand, or enchanting your telescope. seeing through a ghost's transparent body allows you to see how ANY ruin was in the days of its past glory, even jungle temples, pyramids and more. You could uncover some lore elements or even interact with the past through them, acting as portals you can't pass through, but allowing you to steal some items from the chests of the past, maybe you could see their original form in the past. they can't be hit with any item, but they will disappear forever if exposed to sunlight and they are attracted to soul lights or maybe candles (so you can guide them out if you need). if they see you destroying their resting place original blocks, they will haunt you, possessing mobs, turning them aggressive and chasing you, even passive mobs. if the mob dies, they will exit the mob body and still be angry at you. you need to give them echo shards (presumably containing echoes of their past) to calm them down or they will follow you until you die or destroy them with sunlight.
They are afraid of endermen, because of some shady lore linked to the End dimension. Maybe, they were one with them, once.