Darkclaw was a solid, reliable rat captain in the horde of Cluny the Scourge. He was considered by everyone in the horde, himself included, to be the third in command under Cluny and Redtooth; Cluny considered Darkclaw an intelligent Captain.
When Redtooth disappeared in mysterious circumstances (he was thrown to his death by Constance, but Cluny never found this out), Cluny decided to promote the ambitious Cheesethief instead of Darkclaw, though it was a ruse to get rid of an over-ambitious potential rival. The ruse worked perfectly, as Cheesethief was killed by Constance, who thought he was Cluny.
In the aftermath of the siege tower's failure, Cluny temporarily lost confidence, and Darkclaw took charge until he recovered, appointing Fangburn and Killconey as his lieutenants. He tried to get the horde into Redwall Abbey through the tunnel that Killconey had built. Unbeknownst to the rats, Chickenhound had told the Redwallers about the tunnel, and the moles had discovered the exact route. The Redwallers set a trap for the vermin, and the moment Darkclaw poked his head through the tunnel exit, he was saturated by a cascade of boiling water that was poured into the tunnel, instantly killing him. Shortly after his death, Cluny saw Darkclaw in a dream featuring several of his dead captains.