How does thorin disappear?

Answer 1

He was the first one to step out into the open, into the elves' light, and so the magic hit him hardest, and he fell dazed to the ground. The wood elves carried him off with them when they ran away, but the other dwarves and Bilbo were left behind.

Answer 2

Later, the lights appear yet again and they cannot resist approaching them. There is the great feast that Bombur

described from his dream. Thorin steps out and it disappears.