This is the J4CKIECHAN Karazhan Tempo Mage Deck he was playing on stream at high legend rank. Firelands Portal is a great addition to Tempo Mage and strengthens the late game, while having that important spell synergy.
This is a mid to late game heavy deck. I prefer the Tempo Mage decks with more burn and always have a better win ratio with these lists. This is a solid list though, even has Sylvanas Windrunner. So slow it down a little and play a more controlled game than a tempo burn.