Questioner

So we already know that Vasher was Kaladin's trainer with a Shardblade, 'cause you told me that last time I asked you. So does Vasher just have a large mass of Biochromatic Breaths and that's how he's surviving, or is he somehow feeding off Stormlight while he is there?
Brandon Sanderson

He is feeding off of Stormlight, which is the primary reason why he came to Roshar. Investiture is easy to access in plentiful amounts.
Questioner

How did he know how to use Shardblades so well when he got there, is that related to how they created Nightblood
Brandon Sanderson

Yes, he has experience with Roshar from hundreds of years ago.