Saint Elmo's Fire by Mellownite (Patreon)

It is a great day when a Raven Knight first steps foot into the 'Tomb of Sleeping Gods'. It is one of the two secret subterranean architectures that dwell within the Mana Garden beneath the 'Raven's Nest.'

In the Tomb are small monuments and tomes that hold the record of every single Eldeidan that was created by the Druids during the Baptism, as well as a few relics of old. 

Though 200 Eldeidan had been forged, the Order personally only has 92, though they are aware of the locations of 158 of the God Slayer Weapons. Some are the hereditary symbols of  Noble Houses. Some were lost and are in the hands of enemies, kept as trophies, but 42 are completely missing without a trace; though record of what they are and what they could do are still kept in the Tomb.

When a Raven Knight is deemed worthy and reaches sufficient station in the Order, he is allowed to enter the Tomb and claim and Eldeidan of his own. Ravens a great deal of time in the Tomb trying to figure out what weapon 'resonates' with them. Some even spend months, or even years before they find a weapon to which they have an Aetheral Link.

Sir Riyo Vandeleur did not have this problem. 

"It called to me through the flow..." he would claim of Gram the Farslayer.

The zweihander had originally been in the possession of the Shweinan Hero Siegfried von Richthofen. Considered to be the most famous 'Schwertbrecher', he came to serve as a Raven after the baptism of fire.

The Blade had only three masters before Riyo, each 'Blade Breakers' like Siegfried. Having taken up the arte under the tutelage of former First Raven, Riyo's unique Palawan abilities made it easy to excel at that particular school of arcane artes. 

As with Gram's two other successors, the weapon was said to spark and glow when Riyo came near, creating a brilliant discharge of St. Elmo's Fire. Reacting to something inside of the wakaleo.

Though all previous wielders have had an elemental affinity for lightning, others with the same affinity have not had such a reaction with the Eldeidan, So the Order isn't exactly sure what causes the phenomenon, but each wielder of Gram has instinctively been able to wield it to it's full potential with little training.