Goibhniu

Goibhniu, also known as Goibhnie, was an interloper deity who originated from another plane of existence.

Avatar
The avatar form of Ghoibniu was typically that of a large, brawny human,  dressed in smith attire and with skin blackened from working at the forge.

Abilities
Goibhniu, by his own doing, was impervious to harm from physical weaponry of any type. But his main attribute was his tremendous skill in smithing,  creating armor and weapons that few could rival. The weapons he forged never missed their target and could be used to attempt an otherwise impossible strike, though doing so would cause the weapon to either and bring down Goibhniu's wrath in the form of a thunderbolt. He never forged these weapons for anything less than a deity of intermediate power.

One of the things he was known for crafting were special amulets for the very few mortals he favored. Each was designed with a specific spell in mind,  either nullifying it  or reflecting it back upon its caster, and could be used multiple times. The effects of a negated spell would never appear, or (in the case of something solid) would turn to dust. It was impossible to wear more than one of these amulets at a time and attempting to do so would cause all of the wielder's amulets to shatter. However, these amulets could protect more than one person if they were in physical contact with the wielder, allowing protection for up to 500 people.

Possessions
This deity wielded a +5 spear and a +5 warhammer, both of which would almost certainly kill any living creature they struck.

Realm
Goibhniu lived within the Outlands, in the divine realm of Tir na Og. His own divine realm within Tir na Og was known as the Great Smithy, which sat at the base of an exposed hill and extended far deeper into it than could be readily discerned from the outside. These subterranean levels held vast veins of raw ore. The Great Smithy itself was said that the sound of hammers never ceased, either being the work of himself or the army of smiths that worked within the building under his tutelage.

Relationships
Goibhniu once part of a trinity of Celtic craftsmen, with gods known as as Creidhne the Worker and Luchta the Wright. The two both gave their powers to Goibhniu in an effort to raise him to the status of an intermediate deity, thereby becoming his dutiful proxies, in hopes that one day their sacrifice could help them too to rise alongside him.

Though Zeus forbid the Olympian gods from fraternizing with the members of the Celtic pantheon, the Olympian known as Apollo had a secret friendship with Goibhniu. Goibhniu was also occasionally a rival of the Olympian god of blacksmithing, Hephaestus, though because of their unflagging devotion to furthering their craft the two more often compared notes and skills with one another.

Worshipers
The priests of his faith were permitted to wield any kind of weapon, so long as it was made of metal. They wore a kilt as part of their priestly vestments. They had access to spells from the all, animal, astral, charm, combat, creation, elemental, guardian, healing, protection, sun, and weather spheres. They particularly had access to the spell heroes' feast. They also were capable of enchanting any weapon, shield, or suit of armor with a +2 enchantment.

His priests were required to watch over and protect both smiths and warriors, as well as oversee the feeding and healing of the faithful. They were often proficient in blacksmithing, serving as a royal court's armorer or blacksmith.

On Toril, the dwarves of Faerûn occasionally showed reverence for Goibhniu, due to him representing powers of smith-work and the earth, but this was only a rare occurrence.