The Hawk Eternal — David Gemmell

While the warlike and merciless Aenir wreak havoc upon the territory outside the mountain stronghold of the clans, Sigarni, the Hawk Queen, arrives in a parallel version of her own universe through a gate in space and time. Taliesen, last of the gatekeepers, has no idea why she has come. But he knows that heroes are needed and grants her passage into the ravaged land.

Only Caswallon -- loner, warrior, and thief -- realizes the true extent of the danger and the mayhem that his people will come to face. As Taliesen tries to discover Sigarni's purpose, Caswallon must attempt to unite the clans to overcome their greatest peril.