A red orb from another plane, and one of the six artifacts for unlocking Brizoor Waal.

The Red Pearl, found in Myrros, is revealed to be one of six keys for opening Brizoor Waal; - Dragons of the Sunken City (RPA-ADV8)

When traveling to Nebblis, Plane of Fire, the Pearl's temperature directly contrasts the surrounding area;

Your own pack drags you forward toward a patch of red sand between two dark towers of rock. You wrestle it to a halt and discover the red pearl glowing with a soft light. In this world, the pearl is cool to the touch, seemingly still damp from its time in the sea. It levitates behind you, pushing you toward the patch of sand. As you approach, the red pearl glows brighter and grows cooler to the touch. - Gate of Brizoor Waal (RPA-ADVF)

It is later revealed to be the seed of a tree, the bark of which is raw durgolium;

It seems you have planted a seed in this plane, and it quickly takes root. A white-silver tree sprouts rapidly from the red sand. It grows thick and spreads its branches overhead while its gnarled roots crack the stone ground, creating fissures of sand. Into these fissures, the tree drops its acorns, and new sprouts spring up all around you. Before long, you stand in a forest of white-silver trees. Soon, the whole plane will be filled with them. You inspect their bark more closely and find that the trees are made of unrefined durgolium. - Gate of Brizoor Waal (RPA-ADVF)