Sylver is a weasel who has a patch of white fur on his forehead which is shaped like a lightning bolt. He leads a band of outlaws and, later, is the Lord of Thistle Hall. After the humans return to Welkin, he gives up his place as Lord of Thistle Hall. He and his band continue to live in Halfmoon Wood.
Windjammer-Run-port 2-1

Sylver on the windjammer. If you look closely, you can see the lightning bolt on his forehead.

Sylver's best friend is Icham and he admires Miniver's and Scirf's ability to read. Sylver feels responsible when one of his band dies and he is a good, kind leader. He understands his band's feelings well and loves a good adventure.