Cowl

Cowl is a high-octane time travel adventure from Britain's master of widescreen science fiction, Neal Asher.
He's the nightmare you never imagined . . .
In the far-future, the Heliothane Dominion triumphed after a bitter war. But some enemies escaped into the past, to wreak havoc across time. The worst is Cowl – originally human, until artificially-forced evolution made him something else entirely.
Polly is unprepared for her involvement with Nandru Jurgens. He's a Taskforce soldier, now hunted by killers. Nor can Polly resist the alien 'tor' she's compelled to attach to her arm. But when she's dragged through time, she learns fast. Tack has a tor fragment embedded in his wrist – a bloody reminder of Heliothane's government. As their vat-grown assassin, he's no stranger to violence. But the extent of this mission is different.
Meanwhile, a beast hunts its targets through time's alternate dimensions. This is Cowl's pet tor – and it's eager to feed.