Possibly the Greatest Alchemist of All Time season 1 episode 11
Episode title: Signs of Turmoil
Máni joins the Wings of Nolyn as they build the fortress town of Wedgefort, which grows more prosperous by the day. However, the Holy Empire of Sidonia activates their Hero Summoning, which causes the mana in the region to fluctuate, increasing the strength of the monsters outside the fortress' ramparts.
