trusty iron slayer - Roblox Voxlblade 

My friend and I both are on possession builds. Pretty generic ngl.

you need two possession builds to do this otherwise a trusty slayer wouldn't be possible. first the person with trusty perk needs to mark the mob. then the other person who has both part with possession marks it. if done correctly, you can kill the mob while marked by both players and the player with the trusty perk can use the newly possessed mob. that's how. hope this helps

However the possession bug is patched/fix(I already did this with snoeman)

oh. i haven't tried it recently so idk if it still works. if they did patch it, that sucks

Try a possession bug if it's fix/patched

only if you have necrotic handle and possessed blade on a maxed summoner. other than that, trusty slayer on your own isn't possible.