Hoog is a dwarf and member of the Scoia'tael operating in Temeria. Judging by his name, he could be a member of the prominent Clan Hoog, currently rulers of Mahakam.

Zoltan Chivay mentions him as an old friend he was supposed to meet in the Outskirts, but Hoog never showed up. If Geralt kills the Scoia'tael during the Strangers in the Night quest he can ask Haren Brogg if he's heard anything about Hoog. Brogg says he'll ask around but nothing ever comes of this.