Invasion of Gobakhan/Lightshield Array will exile commanders from the command zone. (Historic Brawl)
Invasion of Gobakhan will permanently exile certain commanders from the command zone when casting the back half (Lighshield Array) in Historic Brawl.
This happened to me while playing Errant and Giada every time Lighshield Array was cast. Additionally, this will happen to other commanders, as reported by another user who was playing Samut, Voice of Dissent who had the same issue arise.
What happens is this. Invasion of Gobakhan will lose its last defense counter. The game will then exile it and attempt to cast Lightshield Array. If a certain commander is in the command zone, what will happen instead is the game will present you with a choice. 1: Cast Lightshield Array from exile without paying its mana cost, or 2: Cast your commander. You are still required to pay the costs of your commander. If you choose to cast Lightshield Array, it will simultaneously be cast and exile your commander from the command zone.