Artanis decided that as soon as it retreated that he should leave it to the others in case Mycah would shortly need help as he was the only one up top at the moment. Besides, he reasoned, it's out of the way now. No need to chase after it anymore and waste valuable time that could betray our position to those brigands.

He slung his bow onto his back and climbed up to Mycah's position in case he needed help. However, if the creature was killed and there was no one to menace Mycah he would go down to inspect the creature's corpse and maybe explore the tunnel further.