14: Witch
It did not take long for witches to realize that internal conflicts could not be solved using magic. Generally because anyone with a basic grasp of counterspells could usually get around even the nastiest hexes someone could dream up – so while some witches simply got good at taking their enemies down by hexing them when they weren’t looking (or poisoning them, either way). Other witches realized that someone who sat and studied dusty old tomes all day and all night was probably not keeping up their cardio very well and elected to take a path that was a little more aggressive, and thus witches began to carry blades.
Historically speaking, the first few witches to hit on the idea of tossing magic aside in favor of just stabbing their rivals did a lot of setting the tone for the next few decades of intercommunal violence. The first major coven to become proficient in the art of the sword as well as magic more or less held sway over civilization for nigh-on a century, until armor enchantments advanced to a level that made it a little more of a question of skill. Then came blade enchantments, which got through the armor enchantments, which were improved to become effective against blade enchantments, and everyone realized they might as well just forego the whole rigamarole and fight with unenchanted blades again.
This wasn’t how magic was lost, by the way – but it was part of how it became a less common thing. When a counterspell exists for every spell, they become kind of useless. Power struggles became questions of skill with a blade, or tactical cunning. It was not until the quest for a spell that could not be countered reached its goal that magic was lost, and even then saying magic was lost is something of a misnomer. It is more accurate to say that it was annulled.