Mueller (ミューラー Myūrā) is a boss character in Fire Emblem: Thracia 776. He appears on the 12th turn of Chapter 17A as part of an attempt to ambush the player's forces and prevent them from breaching the gates of Leonster castle. He is a subordinate officer, serving alongside Reinhardt as one of the toughest members of Freege's Gelben Ritter unit. He takes great pride in his position, and defends Reinhardt's name when one of Freege's soldiers questions Reinhardt's loyalty.
Depending on the player's actions during the chapter, he will either get killed, captured, or fail to arrive to the battle quick enough to play any meaningful part in it. Regardless, he is never mentioned again.
Subjective: The following part of this article is subjective to the editor's writing. Therefore, it may not work for everyone.
Mueller's band of Mage Knights will be virtually unstoppable if Cyas is still on the field. Thankfully, Cyas will leave on Turn 15, severely weakening their odds. If the player sends his or her army up north, away from Mueller's spawning position, Cyas will likely leave before any of Mueller's units can even attack the player. Alternatively, the player can use a non-mounted unit with about 11 Defense, a good Magic stat, a Holy Water boost, and a crusader scroll to block off the enemy force before it can cross one of the bridges en route to the main battlefield. The second option has the benefit of allowing the player to thin out Mueller's force without incurring too much of a risk. Mueller's attacking stats are much better than those of his minions, so putting him to Sleep might be a viable option if the player feels threatened by him.
Whatever the case, once Cyas is gone, the battle becomes much easier, but the player must still be careful to avoid getting struck down by the many Thoron tomes Mueller's unit possesses. Despite the poor magic stat of all of its units (generic Mage Knights in this game use growth rates typically associated with physical units), his squad is much more dangerous magically than physically, thanks to the absurd power of Thoron. Using Holy Water is highly recommended,and arming units with crusader scrolls to protect them from critical hits will help as well.
If the player is quick enough, he or she can reach the gate before Mueller even comes into play, bypassing the battle altogether