Thief Guild Master
Players must seek out the thief guild master in order to join the Thieves Guild as well being at least 48 hours old and having a minimum of 60 Stealing skill. Upon joining the Thieves Guild, players may begin stealing from other players in Felucca. On the shards of Siege Perilous and Mugen, stealing is not restricted to the Felucca facet, according to the Siege Ruleset.
The thief guild master also sells the Disguise Kit, but only to characters who are already members of the Thieves Guild.
How To Join the NPC Thieves Guild
Go to any NPC Thieves Guild Master and say the Guild Masters Name + Join (i.e. Elliot join). They will tell how you much. Simply drag the amount onto the NPC and enjoy your new guild benefits.
How to obtain a disguise kit
To get one, a player must locate a Thief Guild Master and say: "(NPC Name) buy disguise kit". The disguise kit costs 700 gold pieces which must be paid for by dropping the payment onto the thief guild master after the buy request has been spoken.