The Bifrost Guardians
Book 2: Shadow's Realm/By Chaos Cursed

Shadow's Realm: When Shadow received a message that Shylar needed his aid, the master thief and his three companions, Allerum and the Dragonmages, Silme and Astryd, immediately set out for Shadow's hometown of Cullinsberg. Driven by Chaos-induced madness, a master of powers far beyond theirs would use anyone and any means to take his deadly revenge on these four warriors of Law....
By Chaos Cursed: For Al Larson it began with his death in a firefight in Vietnam. He woke from death to find himself alive. A mortal man once again, Al found himself caught in a last-ditch fight to save everyone he held dear, as Chaos pursued him into the heart of New York City....