“Dragonslayer” is the Eighteenth Main Story Quest in The Elder Scrolls V: Skyrim
You get “Dragonslayer” after completing the quest “Sovngarde”.
Exit the Hall of Valor with the 3 Nord Heroes. It is time to face Alduin and kill him for good. Head across the bone bridge and approach the edge of the Mists. Wait for the other heroes to catch up after that. When they begin their shout, join them with Clear Skies. Alduin will counter with a different shout that returns the mists. This must be done 3 times before the Mists will fall completely.
Alduin will come flying in after the third dissipation of his Soul Snare mists. Hit Alduin with Dragonrend to make him vulnerable and bring him to the ground. Once Alduin lands is when you can attack him. This Dragon "God" has a number of attacks. All of them are deadly. It is very important to make use of the cover provided in the area. The Dragonborn faces off against Alduin with the aid of the Nord Heroes. They will all be using their shouts to bring this beast low.