The Horn of Jurgen Windcaller

High Hrothgar.

"Rise, Dovahkiin."
"We have taught you what we know - now, it is time for you to discover for yourself your destiny."

"We garb you as the ancient nord warriors of old." He said "Our final gift to you, Dovahkiin."

"As your final test, Dovahkiin." Argneir said. "Retrieve the horn of Jurgen Windcaller."

"I won't disappoint, Master." 

After several days of travel, she had finally stumbled upon Ustengrav, just south east of Morthal.

Freyja delved deeper into its depths, making her way through the draugr dwelling within. 

With a swing of her greatsword, the undead creature shatters and falls to the ground.

In a blink of an eye, the battle is over with not a drop of blood spilt. 

Freyja had finally found the tomb of Jurgen Windcaller, but something was amiss. There was a note.

Dragonborn--
I need to speak to you. Urgently.
Rent the attic room at the Sleeping Giant Inn in Riverwood, and I'll meet you.
-- A friend

"... a friend?" Freyja thought to herself. "I don't like the feeling of  this."

The Sleeping Giant Inn, Riverwood.

"So you're the Dragonborn, huh?" Delphine said. "I have to admit, I'm a little surprised to say the least."
The room was well hidden - it's entrance hidden behind a false door of an old dusty cabinet.
"When I first saw you I thought you were just a pretty face. Well, maybe you are." Delphine continued. "I haven't actually seen you in action.

"I am the Dragonborn." Freyja said. "Why are you looking for me? Who are you exactly?"

"This... may be hard to swallow, but I am part of an organisation called the Blades. We're sworn to serve the Dragonborn."
"You must understand, Dragonborn, I had to go through all that trouble stealing the horn and bringing you here - to be sure." Delphine added. "We're not exactly best friends with the Thalmor. I had to keep my head down."
"We can help you, Dragonborn. I can help you."

"Fair enough. Assuming all you've said is true- how exactly could you help me?"

"We can't. Not right now." Delphine replied. "Right now I'm all that's left of the Blades."
"Most of us have long disbanded or went our separate ways.
"One of our most important members - and my good friend - has disappeared into hiding. If there's anyone who knows how to stop the dragons, it's him."

"... and you want me to find him."

"I wouldn't ask this of you unless it was important, Dragonborn, I can't just show my face - there're too many Thalmor spies. I'm sure you understand."
"His name is Esbern. He's holed up somewhere in Riften's sewers. Last I heard he was in  the Ratway.
"If he gives you any trouble, just ask him - Where were you on the 30th of Frostfall?"

"I'll find him."