The card itself does nothing during the game (which is the downside). But it allows you to include powerful/synergistic non-legendary class cards from 1 other class when you build the Priest/??? deck.

Renounce for neutrals.

A legendary spell for Shaman and a part of his Spell OTK. Point is to return Control Shaman and add a powerful OTK combo to his cheap spells. Imagine this with the new 3 mana Shaman legendary that double casts a spell, the OTK with this card might be over 30 damage if you kill 4-5+ creeps with this spell.  The balance of the card is with the opponent playing around this card but being a t 8 you can throw in 2, 1 cost minions.

"Where you're going, the weather doesn't change."

Ever get that feeling of déjà vu?

Secret mage on drugs

"Made of metal and mind."

Flavor text: "Floop found it so cute at first... Only at first."

Synergy with Treants, and the cost 6 makes impossible to use it and then immediately clean the opponent's treants with Starfall. Also, it follows the idea of the legendary spells of being a dangerous power, that might be a bad idea for the user (like giving minions to your opponent).

Lets say The lich king, Medivh, the Guardian and Ysera is destroyed this way, Chef mech would get The lich kings Attack and Yseras health.

Spoiler shows how Chef Mech then looks like

Attack shout: Dinner is served

Forbearance? You must be new here.

Really cool idea