Are these sentences properly worded?

Gloomwing fell right into the trap and was killed, but not before unleashing a blast of acid at Eldako, knocking the elf under the waves and causing him to vanish from sight. His friends assumed that he was dead and journeyed deeper into the jungle with the cha'asii elves. Eldako was severely wounded by the acid, but not killed, and drifted along in the water for some time.