Power Level 
This name is not powerful in terms of combat ability as Thief has lost even to an awakening Hakram who did not possess a name. The name also prevented the hero from killing when conducting thievery, unlike Assassin which probably encourages the name to kill. The power of this name relies on stealth and thus is more useful for espionage. Thus far Thief has survived a number of attacks and escaped both magical and physical. The Named can also infiltrate heavily guarded fortresses as well as escape when needed.
The Thief role causes the individual to compulsively steal. The Named does not differentiate between enemy or ally as the Thief even robbed the Bumbling Conjurer as well as the Squire's treasury. It seems that the Thief Name is more concerned with stealing often leaving guards unconscious but not killing them. Despite the difficulty of leaving foes alive this is most likely due to the name compelling others to tell of the Thief's deeds, causing the name to become infamous as more gossip surrounds its Named prolific acts.
Special Abilities 
The Thief abilities yield mainly to stealth/infiltration allowing the user to not only launch surprise attacks but to escape unscathed from dire situations. Thus far the Thief has revealed the ability to silence wards preventing alarms as well as traps from engaging. These abilities even helped Squire's troops to infiltrate Diabolist' fortress meaning that the Thief name is also beneficial to non- named yielding to heroic Names, empowering ordinary individuals. The Thief also has the ability to steal objects from individuals, plundering both magical items such as banners that the fae use for their abilities, as well as a sun. The Name also seems to grant access to a special plane to store stolen objects, as demonstrated when the Thief deposited a pile of ships out of her pocket in the first battle of Liesse.