They are giving 1 year free license for the theme away at the hosts website.
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Get UI.X 2 Dark for free by using the coupon code DARKFANFAV during checkout."
Go there and grab it while the promotion lasts.
https://xenforo.com/community/resources/ui-x-2-dark.5866/
UI.X 2 Dark 2.2.10.0.1 Based off the tried-and-true methodologies of its XenForo 1 predecessor, UI.X continues to push the boundaries of intelligent design. With a basis in Google’s Material Design, the framework is backed by a team well-versed in the XenForo software making UI.X a wise choice for any forum. ThemeHouse has been building products for XenForo since day one of the software’s release and we aren’t going anywhere.