Master Londo is Here
Geoffrey had instantly cast disintegration. Since Yumir had lost face for him, he would be reclaiming it by killing Londo.
It wasn't an easy feat for a 16th-stratum magus to instant cast a level-six spell, since those were quite a high level. Quadrupling the mana cost by instant casting was quite a huge burden on magi.
But Geoffrey didn't have to worry about it. That wasn't because he had a far higher mana recovery rate than Annelotte. Instead, he had better equipment that doubled his mana capacity outright!
That was why he could use spells like this without reservation. He had double the normal amount of mana of normal magi. Thanks to this overwhelming power, he fought brashly without bothering with the finer detail and control in combat.