I - Rules
(see JITD, p. 23; FAQ, p. 2)
After making an attack roll, a figure with Sorcery may add 1 to either its range or damage for each rank of Sorcery it has. A figure with multiple ranks of Sorcery may split this bonus between range and damage.
Sorcery versus Ironskin
Sorcery may not add damage to any attack that includes a figure with Ironskin. It may add range to the attack, but not Sorcery. Yes, Laurel can get around this. The damage immunity granted by Ironskin does extend to all figures affected by an attack that includes a model with Ironskin.
II - References
Heroes with the Sorcery ability: none.
Skills granting the Sorcery ability: Wild Talent.
Feats granting the Sorcery ability: Magi Madness (1 magic attack only).
Items granting the Sorcery ability: Magic Bow, Scythe of Reaping, Sorcerous Orb.