Odd-cost deck is a new thematic archetype in The Witchwood, which is supported by some really strong cards. Black Cat is a very similar card to once-staple Azure Drake that had the same effect.
Nothing beats the early draw and spell damage -- both essential elements for Mage's survival. It could easily replace Arcane Intellect as the Mage's usual 3-drop, and put a minion on board at the same time.
The only drawback is that you won't see this card on Arena, as all cards with odd-cost effects are eliminated from the drafts.