Are these sentences worded correctly?

Solostaran agreed to allow Gilthanas to lead the Heroes of the Lance to Pax Tharkas in an attempt to undermine Verminaard and free the prisoners held within the fortress, providing the elves with the time necessary to complete the evacuation of Qualinesti. During the journey, the group was joined by Laurana, and they also encountered Eben Shatterstone, a human warrior who had been Gilthanas’s ally in the past and decided to join the party.