Sealord of Braavos
From A Wiki of Ice and Fire
Many years ago Prince Oberyn Martell travelled to Braavos where Viserys Targaryen and Daenerys Targaryen were being kept by Ser Willem Darry. Oberyn and Willem signed a secret pact, which the Sealord of Braavos witnessed, promising Viserys the hand of Arianne Martell in return for Dorne's help in claiming the Iron Throne. The name of the Sealord who witnessed the pact has not been mentioned.
A Game of Thrones
Syrio Forel tells Arya Stark that Braavosi captains bring exotic animals to the Sealord. His menagerie includes striped horses, great spotted things with necks as long as stilts, hairy mouse-pigs as big as cows, stinging manticores, tiger that carry their cubs in a pouch, and terrible walking lizards with scythes for claws.