In the lagoon by joseph conrad what causes arsat to risk everything

The fact of losing her wife Diamelen, seemingly because of the malaria, was reason in Arsat to desire wants to risk everything, the desire to fight in opposition to his fears and internal demons and to prepare himself to avenge the death of his brother, of the one that Arsat was feeling guilty for not having gone in his help

Found him! the panda is in the middle to the right