Plus, there's the fact that the White Walkers would have been able to kill the gang easily. Jon Snow was outnumbered and at the mercy of the elements. There wasn't much on his side that would have helped him if the wights started to attack — other than those dragons. By luring them over, the Night King has perhaps finally achieved a crucial part of his plan. We already know that, for some reason, they had those chains at the ready , so even if they didn't know when they'd be pulling a dragon out of the depths of a lake, they clearly knew that one day they would.