The eldest of the three Bronzebeard brothers, Magni was destined to be the king under the mountain. Strong of arm and keen of mind, Magni loved his two brothers above all else in the world. From the time of his youth, Magni the prince was keenly aware of what would be expected of him in the future. This apparently intimidated him and he questioned if he could be the kind of leader Ironforge needed. He even privately wished that his father and brothers would outlive him, and thus their people would have a good king. To look upon the tower of strength and effective leader that King Magni is today, one can scarcely imagine that he was ever a prince full of doubt.
He was one of the heroes during the Second War , often directly leading his people into battle. Upon the liberation of Ironforge by the forces of the Alliance of Lorderon he pledged his kingdom's support, his two brothers accompanying the Alliance host.
During the recent fall of Kingdom of Lordaeron, his middle brother, Muradin, was reportedly slain in Northrend. Prince Arthas Menethil sent a letter to Magni stating that Muradin was slain by undead, but thanks to his sacrifice Arthas was able to obtain Frostmourne and would be returining to Lordaeron shortly. The letter also indicated that Muradin's body would be returned, though this never happened. Eventually, Magni learned the truth: that Arthas himself was responsible for Muradin's death. Magni was overcome with grief at the news of Muradin's demise, but he and the youngest brother, Brann, remained steadfast in their desire to continue serving the dwarven people.
After Muradin's apparent death High Inquisitor Fairbanks and Alexandros Mograine visited King Magni. To avenge Muradin, Magni forged the Ashbringer to oppose Frostmourne, Arthas, and the undead. While Magni never took much stock in the belief that Master dwarven blacksmiths could impart emotions into the weapons they create, standing before The Great Anvil, he found himself thinking of how he would not see Muradin again. He thus harnessed all of his rage, fury, the desire for vengeance, and willed them into being with each strike of his hammer. When he was finished, he gave Mograine the finest blade that had ever been crafted by his hand. This would confirm that he is, at the very least, a skilled weaponsmith of the highest degree.
Brann, an explorer of some renown and brother of King Magni, went missing for months, and King Magni had lost hope that he still lived. Though he remains a wise and strong leader, his pain and sorrow weigh heavily upon him. Many dwarves wonder whether the kingdom will ever see another Bronzebeard sitting on the throne of Ironforge. Recently, the intrepid Brann popped up once more, seeming to have survived his Silithus venture and somehow getting the base of Atiesh into C'Thun's otherworldly carapace. Much to Magni's dismay and a series of agonized groans from the Explorers' League, Brann has again managed to misplace himself within Outland and recently again in Northrend.
King Magni's only child, Moira Bronzebeard, was captured by Emperor Dagran Thaurissan, and was thought to be kidnapped while under a magical spell.
During Bolvar's tenure as regent of Stormwind, Magni diplomatically approached Stormwind for assistance against the ever increasing Dark Iron threat, citing their destruction and control of Thandol Span. Much to his frustration, his pleas fell on deaf ears. While Bolvar concurred with the dwarven king, Lady Katrana Prestor, advisor to the recently returned King Varian, accused Magni of trying to involve Stormwind in the dwarves' personal war, and refused to send reinforcements. Luckily, Jaina already informed Magni of the appearance of Lo'Gosh, who was also thought to be the real King Varian Wrynn. Lo'Gosh and his companions attacked the Dark Iron Dwarves, later Magni and his dwarves helped him, and together they defeated the Dark Iron that had controlled Thandol Span.
Magni later sent a team to assassinate Emperor Thaurissan and retrieve Moira. When the team sent word back, he was shocked to discover that Moira refused to return to Ironforge and that she and Emperor Thaurissan had in fact, fallen in love. He also learned that they had conceived a child. Much to the kingdom's despair, Magni's grand heir will apparently be a dwarf who is both the heir of the King of Ironforge and the Emperor of Blackrock.
In a nightmare caused by the Emerald Nightmare, Magni dreams that he leads a team through Blackrock Depths to rescue Moira. In regards to her son, it seems that while he accepts that the child will be born, it would be banished forever from the kingdom. He would not allow a son of Dagran Thaurissan to inherit the throne of Ironforge.
In World of Warcraft
King Magni Bronzebeard was a Level ?? (Boss) quest giver located in the High Seat
in the Great Forge
in the dwarven capital city
He started the following quests:
He ended the quest  The Feast of Winter Veil ( Feast of Winter Veil).
Wrath of the Lich King
This section concerns content exclusive to Wrath of the Lich King
Magni also appears briefly at the frost dwarf stronghold of Frosthold in the Storm Peaks during  The Brothers Bronzebeard.
[Prince Magni Bronzebeard's Silver Coin ] can be fished from the Dalaran fountain. It bears a wish from when he was younger: "I hope that my father and brothers outlive me. I'll not make much of a king."
This section concerns content exclusive to Cataclysm
He was present at the Elemental Unrest meeting in Stormwind and informed the other Alliance leaders about the Tablets of Ulduar. During the exploration of Ulduar, the dwarves found a set of mystical tablets created by the Titans. During the Elemental Invasion, Magni protected the Commons of Ironforge from the Elements.
Activating an Ulduar tablet to protect his people from the Cataclysm, King Magni Bronzebeard fell prey to a terrible curse that fused his statue-like form into the diamond heart of Ironforge itself. To compound this tragedy, Magni's estranged daughter Moira returned, claiming her father's throne for herself and for her infant dark iron son. In an effort to prevent further political turmoil, the Council of Three Hammers was established to succeed Magni.
On the Azeroth's Fortune mini-game page of the Cataclysm homepage, one fortune implies that Magni activated the tablet by speaking Kalimag (although the titles can be randomized with the fortunes).
When the winds scream and the stones shudder, the mountain king shall look to the earth for reasons why. He shall taste the soil beneath his feet and ask its advice in a tongue no longer his own. In reply, he shall be made one with his past and transformed into a paragon among mere stone.