As a magic user, your power bounded to magic stone, where you couldn't do anything without it, but as a Serafim, it was different story entirely. Your divine power allowed you to have limitless power, you didn't need such a thing like magic stone to support your power and the Sylph was a natural protector mythical creature.
They only had around ten magic users that came from the Holy Kingdom after the last attack of the monster and Nefilim in the Golden Light pack, more so with everything that had been going on, the supply of magic stone dwindled drastically. It was hard to find those stones nowadays, since there were attack after attack and power struggles.
Magic stone was scarce, even more when they learned the Red Claw pack had fallen into the enemy's hand.