- After offending the Thieves Guild, wait for them to calm down.
- Talk to Vex and obtain 1,000 gold.
- Pay your way back into the guild.
You get this quest for offending the Thieves Guild, usually by assaulting/murdering one of their members, attempting to steal from them and getting caught, or murdering someone during a guild quest. This will result in an expulsion, meaning no more training sessions or fencing services, and limited conversations with guild members. To rejoin the guild, speak to Vex in The Ragged Flagon, who will reprimand you and demand 1,000 gold as reparations. Return when you have the money and you will be let back into the guild.
If you've been expelled for assault, you may need to wait 48 hours outside the Ragged Flagon for hostile guild members to calm down.