When Aenarion defeated the forces of Chaos at the shrine of Asuryan, Caledor was among the first to proclaim him as the chosen champion of Asuryan. Together, Caledor and Aenarion made their way to the Anvil of Vaul, where with the Hammer of Vaul they forged the Great Weapons that would be used to combat the forces of Chaos, as well as artefacts such as Aenarion's Dragon Armor. After forging the Great Weapons, Aenarion and Caledor sent out a call to the mightiest warriors of the Asur, and those who gathered at the Anvil under the banner of Aenarion were gifted each a Great Weapon, becoming the future Princes of Ulthuan.
When the Second Great Chaos Incursion occurred, Caledor Dragontamer had a falling out with his friend, Aenarion, as he urged him not to draw the Sword of Khaine. The great mage foretold that drawing the sword would cause great sorrow to the Asur and to all of Aenarion's line. While Aenarion carried on the bloody fight against the forces of Chaos, Caledor Dragontamer set up a plan to use the ancient Menhir Stones (focus points of magical energy) around Ulthuan to drain off Chaos energy of the Aethyr which was spewing into the world from the collapsed Chaos Gates at the poles, enabling creatures of the Realm of Chaos such as daemons to manifest in the physical world with ease and assault the Elves.
Unfortunately, the energy required was so great (despite the Slann in Lustria lending their powers to the effort) that it caused the entrapment inside the Vortex of all the High mages (Including Caledor) of Ulthuan, while Aenarion gave his life buying time (battling a great Chaos war host) for the plan to succeed. The plan eventually created the "Vortex" on the Isle of The Dead at the centre of Ulthuan which drains magical energy from the world. However the plan was only partially successful, while the Chaos energy is drained away, it continues to spill from the Realm of Chaos and it particularly high in concentration in the Chaos Wastes. And as if some horrible joke of the gods, for their success Caledor and the rest of the mages were trapped inside the vortex, not dying but suffering a fate worse then death, eternal imprisonment.