A pure thief does not get into battles, but sneaks or runs by them. That is why a Pure Thief is such a challenge. Most people play a Thief who has some combat skills.
I have a thief with points only in Sneak, Lockpick, and Pickpocket.
No weapon skills, no magic, no potions, and no armor.
All the level points go into stamina....for running away.
Level 27 with about 70 hours played and zero kills.
Because she doesn't kill there is some content she'll never see...but it's a fun challenge.