Infernal Sorcerer Heritage( Player's Handbook II, p. 91)
Your innate magic derives from infernal ancestors. Your blood is thick with their power, allowing you to exhibit a variety of abilities.
Sorcerer level 1,
You gain a bonus on saves againstfireand poison equal to the number of infernal sorcerer heritage feats you possess. When you use a conjuration (summoning) spell to summon an evil outsider, you gain a +2 bonus to your caster level.