Another Tri-Class card from Mean Streets of Gadgetzan revealed at Blizzcon was this Kazakus HS Legendary Tri-Class Card.
The card reads: Battlecry: If your deck has no duplicate, create a custom spell.
This card is pretty insane. You get to create a spell by going through a couple of options. Giving you more choice and power in the discover mechanic than previously seen. An interesting new mechanic coming with the new expansion.