What is the best way to deal with someone stealing from
you ALL THE TIME? PS I am not a duergar.

Pretty sure the inn has some funky stuff in place for stealing.

Go sit on the water. Can't steal from you that great if you are bashing them.

Go sit at the entrance of forest areas and spam bash or trip or whatever.

Basically treat them how you'd treat assassins stalking you.

ORRRRRR...

RP with them and get them to stop stealing from you via becoming fiernds.

Stay out of civilized areas.
Keep nofollow players on.
Stay on water.
Faerie fog or area of effect damage at random times to pull them out.
Make friends who see hidden.
Use wearable containers.

Make sure you move fast when in civilised areas.

If you've been in an area for a long time (eg ugruks) then leave by an exit other than eastern road.

Put your stuff in a wearable container and wear it.

Don't always quit out in your cabal and then spend a while looking in the cabal chests when you log on, then leave from your guild.

Do try to catch the thief depending on his build. For example, right outside hamsah gates he will step from hiding and he can't see you are there unless he scans, because it is a separate area. That's where the shaapamatic 4000 used to annihilate thieves and assassins.