Runecraft

Runecraft is the original magical art used by the dwarves long before the introduction of Rank Magic.

Background
Two hundred years ago, runecraft was the traditional art practiced by the dwarves of the Dwarf Kingdom. However, after the Demon God Unrest, the art had become nearly extinct. It furthered declined into oblivion when younger generations of dwarves began abandoning its use in favor of the more practical and effective Rank Magic.

Mechanics
Runecraft is the art of inscribing magical letters onto objects. When a rune is carefully engraved, on an object it enchants the object. The amount of magic inscribed in an object depends on time it takes to inscribe a rune.

There are 50 lesser runes, 25 middle runes, 10 upper runes, and 5 top runes, for a total of 90. That said, many of them have been lost, and only a few are left. Exactly how many secret and divine-class runes there are is the stuff of legends.

Runes apparently were abandoned due to several disadvantages. Compared to Rank Magic, which could enchant an item in a near instant, runes required time, thus using it in full production was not cost-effective. In addition, only runesmiths are able to create and utilize runes, and the number of dwarves capable of becoming runesmiths is said o be even smaller for those capable of becoming magic casters. However, runes possessed advantages not found in the Rank Magic system, such hardly possessing any material costs.

Ainz Ooal Gown theorizes that runecraft may have originated from YGGDRASIL, and that perhaps the runecraft system was never discovered by players due to its obscurity.

Trivia

 * Some runes used by the dwarves are recognized to be the same as the runes from Satoru Suzuki's world.
 * The runesmiths of Dwarf Kingdom stated that only a number of six runes has ever been known to be successfully embedded into a single weapon during the peak of the craft.