How do we know about Frost?

[matt1.]

I gather that Hoid’s letter in The Way of Kings is addressed to Frost. How do we know this? And even more, from what source do we even know there is someone called Frost?

I’ve read all of Mistborn, Elantris, Warbreaker, Arcanum Unbounded, and Stormlight as far as Oathbringer. Have I missed something? 

[Bejarden he/him]

Brandon did a reading with Frost meeting Hoid:

https://wob.coppermind.net/events/332/#e9518
It’s mostly Cannon 

[Honorless he/him]

Frost is also a character present in Dragonsteel Prime

https://www.brandonsanderson.com/dragonsteel-prime-chapter-25-bridge-four-1/

[matt1.]

2 hours ago, Bejardin1250 said:

Brandon did a reading with Frost meeting Hoid:

https://wob.coppermind.net/events/332/#e9518
It’s mostly Cannon 

 

2 hours ago, Honorless said:

Frost is also a character present in Dragonsteel Prime

https://www.brandonsanderson.com/dragonsteel-prime-chapter-25-bridge-four-1/

Thank you both. This is much appreciated!

[Weltall]

In addition to the previous points, we had WoBs that confirmed that Frost was the recipient of the WoK letter years ago (here and here) by combining the two pieces of information that Frost is the oldest character we know and that the letter was written to somebody older than Hoid. Oh heck, just follow this link to Arcanum and go down the list of WoBs we have on Frost and you'll know almost as much about him as anyone not named Brandon Sanderson does. xD