Jasher is one of the Amar Kabal. He helps Jason and Rachel during the events of the first book, and accompanies Jason on his quest during the third book.
Known Background
Jasher was known to have served Galloran before he was captured, and he was an exile of the Amar Kabal. He declined all three invitations to Harthenham, which made him wanted by Maldor.
He was sent by Galloran to assist Jason and Rachel in their quest for the Word, and rescued them when Maldor's men attacked them on their journey to see the Pythoness.
Family
Jasher has a few relatives mentioned in the series. One is his wife, Farfalee, a son named Lodan, and his brother-in-law, Drake. His brother Radolso was also mentioned twice in A World Without Heroes, it said his seed was destroyed by a displacer working for Maldor.
Death
It is unknown how many deaths Jasher experienced before the series' beginning, but he dies twice in the series. In A World Without Heroes, he explodes when Kimp accidentally strikes the orb of orantium Jasher was carrying, and in Chasing the Prophecy, the Wanderer kills him. Both times, his seed remained undamaged and he was safely replanted.