Hi all.

I'm working on converting a few monsters into 5e from older editions, specifically the loumara family of demons who specialize in possession. The dybbuk is sadly the only one to receive an official conversion. This brings me to the question: of all monsters who have the possession ability (including the ghost, yakfolk warrior, tsucora quori, etc.), have you seen any possession ability or something similar on another monster that doesn't immediately assume control of the host?

The reason I ask is that the guecubu, and many movie demons for that matter, possess a host and act as a rider, tormenting the host but not always explicitly taking control of their body.

Thanks

I think the design pattern for 5e would handle this as simply a condition that you could flavor as possession. For example a creature might give you the frightened status as it torments you from within your mind. Ultimately you break it down into the mechanical effects you want the possession to inflict (which is usually "dominated" but doesn't have to be), and then just describe it as possession.

You might look at the spell dream for ideas.

I'm also looking at a few creatures that have abilities that attach them to another creature, like the wretched sorrowsworn's bite. The puppeteer parasite and necrichor are also very promising.

following that theme, these guys might be what you need.  https://www.dndbeyond.com/monsters/17163-intellect-devourer