I dont mean a guild or clan, i mean an underground place, with a little man behind glass who you ask who needs hitting.
He gives you the picture, you go find the person and kill em.
In Era, this would be an NPC which is randomly roaming in a building or down a street. Return with a photo of the person you killed as proof, claim your prize.
Now that, would rule
...well its a small interesting addition to blow some brains.