+2 racial bonus to hide and bluff. Ability to cast darkness once per day as a 5th level sorceror or as their character level, whichever is higher (I ammend this to give every Tiefling access to a 2nd level spell- so some might have darkness, some might have.. web or something).
Wow, I feel so priveledged to be the one answering this.
It's right in the MM, page 151 (planetouched entry).
Tieflings get +2 INT, +2 DEX, -2 CHA can use darkness once per day as a supernatural ability (favored class: rogue). They also get a +2 racial bonus to to bluff and hide checks.