The Sunhammer was a Callieach designed artifact of immense power, able to harness the power of the sun.
During the Wind Age, the great hero Connacht the Wolf asked the Smiths of Muirthemne to create the Sunhammer for the purpose of defeating the Trow. Forgemaster Traval stated that such a device was beyond their skill until Connacht presented him with the very thing need to make the artifact, a Callieach Heartstone recovered from the remains of the Rod of the Callieach.
After months of construction, the Sunhammer was finally finished, but before it could be put to use, the Spider Cult attacked the forge, killed many of the smiths and stole the Sunhammer along with another artifact, the Tain.
However, the remaining smiths infiltrated the spider temple, recovered the stolen artifacts and defeated the cult and their spider god before imprisoning themselve within the Tain to prevent Syrkrosh from ever returning.
Connacht decimated the trow temple cities with the recovered Sunhammer, harnessing the power of the sun to melt their cites to the ground and imprison the giants in molten iron. It was here that the trow's brutal grip on the world was ended.
During Connacht's reign as emperor, he instructed Damas to find all the artifacts of power, including the Sunhammer and Tain, destroy the ones he could, and hide the rest so that The Leveler could never gain possession of them during the next cycle, in which Connacht knew he would return as Balor.
The Sunhammer was either destroyed or remains hidden to the present day.