Mulligans
General Mulligans
You want to keep your ramp cards Wild Growth and Mire Keeper, while Wrath allows you to cycle, Living Roots gives you some minions.
This is a Yogg-Saron deck that combines thre other Druid Yogg decks that I saw; I didn’t have some of the more expensive cards (Cenarius, Fandral, Wisps of Old Gods), but I was still able to combine the three decklists and replace those cards that I don’t have.
Since you have Emperor Thaurissan, you need more card draw than the standard yogg druid, which is why I include cards suck as Gadgetzan Auctioneer Nourish and Azure Drake.
Links to other decks so you can see their decklists and their reasons for having certain cards:
http://www.hearthstonetopdecks.com/decks/miracle-yogg-saron-druid/
http://www.hearthstonetopdecks.com/decks/ciphers-yogg-saron-druid-june-2016-season-27/
http://www.hearthstonetopdecks.com/decks/j4ckiechans-yogg-saron-token-druid/