Gyras is a protoss planet located near the Koprulu Sector and a famous battleground during the Aeon of Strife, battles repeatedly being fought on the planet's proving grounds. This claimed the lives of thousands of protoss warriors and only ended with the coming of Khas.
Afterward the ruins were sanctified as an arena of honor.
1998-10-23. Proving Grounds. StarCraft Compendium Map Archives.