It ended over 10 years ago probably and the ending involved a giant mana sword the diameter of the world. It was one of those save the world type of mangas (at the end) in a fantasy, nonearth setting.
One of the main protagonists is a tall, big boobed witch (probably? Something like that). They protagonist group had to complete 4 trials or something and one involved a dragon in a volcano. This is all my vaguely guessing from memory.
that's about more than 1000 manga with the same detail. if you remember anyother tags besides magic use this site might help find it. https://www.anime-planet.com/manga/tags/magic