Legacy of the Forlorn
When in combat this weapon functions as a +1 adamantine flaming greatsword. The inner heat from the obsidian grants it the flaming property. When used by someone under a rage effect, the sword becomes a +3 Flaming Burst greatsword. This lasts until the rage has expired.
This 7 foot long piece of obsidian was cut and crafted into a great sword some time ago. One edge is impossibly sharp while the other is smooth and wide. The hilt is crafted from some type of bone, and the bindings holding the chunk of obsidian onto the hilt appears to be animal sinew. This blade is always hot, so much so that when used in combat it sears the flesh of those struck by the blade. Currently this weapon is being used by a barbarian called Magnus Samuelsson, Slayer of Torbjorn, and he is attempting to slay a Linnorm to gain a kingship in his lands far to the north. Local gossip suggests that when Magnus is in the grip of rage, the shard of obsidian actually erupts with lava in the same manner that the volcano that birthed it did so long ago. The hilt is actually made of Linnorm bone, and the sinew is the tendon from that same creature.