Airgeatlámh is a Legendary Artifact that Rou found in Velvet's tomb, it is a prosthetic arm made of silver and magically enchanted.
It is indestructible and has many interesting magical abilities that Rou can use to cause devastating effects:
Name: [Silver Artificial Arm - Airgeatlámh]
Rank: [Legendary] Class
Ability: [Armblast] [Spellblast] [Self-Evolution] [Elemental Echo]
Details: A divine artificial arm previously worn by Velvet found in the depths of a certain ancient dungeon. Those who lost an arm can obtain an arm that they can equip and with it perform any movement flawlessly.
By taking in other kinds of metal, it is possible to change the shape according to the wearer's intent, this ability improves with each use. Destruction of this item is fundamentally impossible.
Upon attachment it becomes able to transmit sensations of touch as well as allow the wearer to use his abilities in that arm like normal.
History under Rou's Ownership:
In combat Rou tends to use the arm as an indestructible shield. Also, due to its indestructibilty, his punches and stabs with it can penetrate even the hardest of monster shells and scales.
In the workshop, Rou frequently uses the arm's metal absorption ability to absorb rare metal ingots such as mythril and then excrete multiple synthetic copies of the metal to be used as resources for the blacksmiths.
When Rou first attached the arm, as well as each time he ranks up, Airgeatlámh's self-evolution triggers, resulting in the arm adjusting to fit Rou's size. It even spreads to the additional arms Rou gains upon rank-up to Vajrayaksa Overlord.
On day 93 Rou mentioned he had used synthesis to add his Fluid Restoration ability to the silver arm's list of abilities, allowing it to store up blood for use later, primarily as part of an ultra high speed recovery technique allowing a complete instant regeneration of Rou's body.
On Day 292, Rou uses [higher analysis objects] and discovers that the arm had become a part of him and upgraded to a [[[Phantasmal]]] Class Artifact when he first Ranked-Up to a Vajrayaksa Overlord and was infused with divine power, explaining why it spread to his other arms.