|Alias||The Sea Lion|
|Died||In 134 AC, Great Wyk|
Leo Costayne, known as the Sea Lion, was a knight of House Costayne and lord admiral of the Reach during the reign of King Aegon III Targaryen.
Aged in 133 AC, Leo was a grizzled seafarer.
In 133 AC, when Lord Alyn Velaryon was dispatched to the westerlands to battle Lord Dalton Greyjoy, twenty Hightower war galleys commanded by Ser Leo joined the Velaryon fleet. However, Dalton was slain before the fleet arrived and the his ships returned to the Iron Islands. With their fleet destroyed, House Lannister was reluctant to see the Velaryon fleet depart in fear of the ironborn returning. Until the Lannisters and Farmans could rebuild their ships, Alyn agreed to allow a third of his own fleet remain in the westerlands, under the command of Leo.
While Alyn had refused to attack the Iron Islands, Leo proved more amenable to Lady Johanna Westerling, the Dowager Lady of Casterly Rock and regent for her young son, Lord Loreon Lannister. Swayed perhaps by Johanna's promise to marry him if he conquered the Iron Islands for her son, Leo invaded the isles with his fleet in 134 AC. In the middle of the ironmen's struggle for power, Leo and his army took them unawares and put many to the sword, landing thousands of Lannister soldiers on Pyke, Great Wyk, and Harlaw.
Ultimately, Leo was killed by Arthur Goodbrother in the hills of Great Wyk. Leo's host was largely destroyed and three quarters of his fleet were seized or sunk, but a portion of his fleet returned to Lannisport with highborn captives aboard. Amongst the notable hostages was Rodrik Greyjoy, a salt son of Lord Dalton that Lady Lannister would geld and make her son's fool.
- ↑ 1.0 1.1 1.2 Fire & Blood, Under the Regents - The Voyage of Alyn Oakenfist.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 The World of Ice & Fire, The Iron Islands: The Red Kraken.
- ↑ 3.0 3.1 3.2 Fire & Blood, The Lysene Spring and the End of Regency.