Had a chara, who famously had the nickname the Troll of Red Bridge, and people think he is called that because he is ugly like a troll and is from Red Bridge. It is partly true, but it's because he defended a village for 3 days without rest, he always asked the bandits to pay the toll, which was all their weapons, but the bandits never complied and always died on the bridge.
No... I think it's on my G drive somewhere...
It's just some generic isekia book...
It's a post-magic world where there is a big "plug", so there is no magic energy, and it happened because mages are A-holes.
So, mages hole up with "magic batteries" in hiding and continue to be A-holes in secret.
MC is part of a group that hunts mages and destroys magical artefacts (Fallout Bro steel?)
The group have no magic, gets power and is favoured by luck, by making oaths/destiny to the world.
Your promise has to be an honest desire/
e.g to be a good husband, you are blessed and excel in learning husband-related skills. You get an itch constantly to fulfil the oath, but if you ever get married, i.e., be a good husband, your destiny is fulfilled and loses buff and luck. There is some loose loop hole on what is a husband skill
MC the Troll, Oath is to be someone who can make his mentor proud. The story is about completing a quest that his mentor died trying to complete, and how she died.
End with the mc competing his oath losses his power buffs, but inadvertently returns magic to the world.
It was called Oathkeeper or Oathbearer, but Oathkeeper is a far-right anti-government militia that did an attack on the USA Capitol on Jan 6, so... yeah..