X-23 is the card that caught my eye the most in Age of Apocalypse. Having 3 ATK for 1 consequential damage puts her well above rate for a 3-cost ally and plays extremely well with healing effects like First Aid and Reinforced Suit, turning every point of healing into 3 extra damage. X-23's readying ability is also excellent for an ally healing strategy, which tends to be highly efficient on a resource per damage basis but can otherwise be very slow to use up that ally's hp. Even if X-23 just attacks twice and blocks, you still get a great deal, and unlike many of the best allies in the game, that value is pretty agnostic to different scenarios that can vary in minion count, have a steady/stalwart villain, or require your deck to build around it somewhat. With a high floor and high ceiling, I expect X-23 to be a new staple ally for leadership!