Leo Costayne

Ser Leo Costayne, the grizzled seafarer known as the Sea Lion, commanded House Hightower’s galleys in Alyn Oakenfist’s fleet and later led a costly Lannister assault on the Iron Islands. His death on Great Wyk, where three-quarters of his ships were seized or sunk, marked the failure of the effort to deliver the islands to Lady Johanna Lannister’s son.

Identity and Naval Command

Costayne was an experienced seafarer whose reputation earned him the name the Sea Lion. In 133 AC, when Alyn Oakenfist finally left Oldtown rather than wait any longer for Lord Redwyne’s promised galleys, Costayne commanded twenty war galleys of House Hightower that joined the Velaryon fleet. The ships followed Oakenfist down Whispering Sound and into the Sunset Sea.

The Iron Islands Campaign

During the struggle for power that followed Lord Dalton Greyjoy’s death, Costayne took a different course from Oakenfist, who refused to join House Lannister’s campaign of vengeance against the ironborn. Costayne was more receptive to Lady Johanna Lannister’s appeals and descended upon the islands with his fleet, landing thousands of Lannister swords and spears on Pyke, Great Wyk, and Harlaw. The account suggests, without establishing it as certain, that Lady Johanna’s promise to marry him if he could bring the Iron Islands under her son’s rule may have swayed him.

Death and Outcome

Costayne could not accomplish that objective. He was killed in the stony hills of Great Wyk by Arthur Goodbrother, and three-quarters of his ships were seized or sunk in the cold grey seas. Although the Lannisters inflicted severe losses on the ironborn, the defenders of Pyke beat off their assault, and Toron Greyjoy remained on the Seastone Chair. Costayne’s defeat thus joined a devastating Lannister reprisal to the failure of its intended political settlement.