Possibly the Greatest Alchemist of All Time

Season 1, Episode 11: Signs of Turmoil

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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.