No I in Team (3.5e Flaw)
From D&D Wiki
No I in Team
Who ever said those posters were good for you.
Effect: When separated from allies or forced to go solo, you suffer. For every square between yourself and the nearest ally take -1 to all saves. Whenever you break off from the team to do something you must make a will save (dc determined by the difficulty of the action).
Roleplaying Ideas: Maybe you're a goody two shoes, maybe you're just needy. Regardless, you need them more than they need you.