The Phoenix Stone was a powerful artefact from Mulandir. Inside this seemingly indestructible stone lies the legendary Phoenix made out of Allfire. According to legends only a blade not of this world was able to break through the shell of that stone.

SpellForce: The Order of Dawn

After the rune warrior that was awoken by Rohen in SpellForce: The Order of Dawn got the Phoenix Stone from Mechlan in Mulandir, she became known as the Phoenix Bearer because of her posessing the stone. She attempted to get her hands on it to use the power of the stone against the Dark One but he surprised her and Sartarius in the Southern Godmark and took the stone from her. In Sharrowdale the stone was used by the Dark One to power a portal with magic power that allowed him to travel back in time before the time of the Convocation.

SpellForce: The Breath of Winter

Not much was told her except for the fact, that the Phoenix Bearer was still carrying the Phoenix Stone after having taken it from young Rohen's Time Portal.

SpellForce: Shadow of the Phoenix

The Dryad of the Life Tree told the rune warrior, that only a blade not of this world would be able to break the Phoenix Stone and thus be able to release the Phoenix. The Phoenix Bearer and Shadow Warrior used said prophecy of the Dryad and were able to destroy the stone and free the Phoenix with the help of the the Shadowblade. Burning with rage at the mages of the Circle that once put it inside the stone, it obliterated the revived Circle and Hokan Ashir in the Bone Temple of Zarach.