Well, the way I see it? The party of 1st level characters can run from the wyvern, the same wyvern they saw fly overhead a half-hour ago headed in this direction, also the same wyvern the townsfolk warned them about, and was obviously placed here to push them toward Yonder Convenient Dungeon Entrance clearly visible and only 30 feet away, so that we can all begin tonight's adventure...
...or they can plink at it with their dinky swords and cantrips, getting annihilated one by one, and glaring at me the whole time like I had broken the law or something.
Guess which one the players chose?