In which book you mean? In the first book, at the beginning it's Redtail.
Add'l: From the beginning of the series, ThunderClan has had the following deputies: Redtail (Into the Wild; deputy to Bluestar; deceased), Lionheart (Into the Wild; deputy to Bluestar; deceased), Tigerclaw (Into the Wild - Forest of Secrets; deputy to Bluestar; exiled; later ShadowClan leader), Fireheart (Forest of Secrets - The Darkest Hour; deputy and successor of Bluestar), Whitestorm (The Darkest Hour; deceased), Graystripe (The Darkest Hour - Sunset; absent from Dawn - The Sight; deputy to Firestar), and Brambleclaw (Sunset - present; deputy to Firestar).
thunderclan cats :|
The second leader of Thunderclan was Owlstar.
This is not likely. After all, the entire series is set in Thunderclan.
That person is called a Traitor.
Onestar wanted a war with ThunderClan because he thought ThunderClan stole WindClan's kits, and he wanted them back.
yes, he was a traitor, he went a long with Benedict Arnold who was a traitor
Brightheart is from ThunderClan in the Warriors series by Erin Hunter. She is a warrior in ThunderClan and is known for her bright, intelligent personality despite her physical scars.
Traitor
A female traitor would still be known as a traitor. There is not a gendered term.
he is a traitor. Traitors are punished very harshly.
Jayfeather belongs to ThunderClan and his parents are Leafpool of ThunderClan and Crowfeather of WindClan.
Leafpool became a normal warrior in ThunderClan.