From A Wiki of Ice and Fire
The Witch Isle is one of the threescore islands off the eastern and northern coasts of the Vale of Arryn. It is the seat of House Upcliff, who have a sinister reputation.
The Witch Isle was brought under the rule of House Arryn by the marriage of Alester II Arryn, King of Mountain and Vale, to Arwen Upcliff.
- ↑ 1.0 1.1 The World of Ice & Fire, The Vale.