Instructions
Join a guild. To find a guild accepting new members, visit the larger in-game towns such as Prontera and search for bulletins posted above fellow players' heads. Guilds not only recruit in-game, they also advertise on public websites, such as "Ragnarok Online's" official forum.
Collect the following items: 30 Stones (dropped by Megalith in Ruande), 1 Oridecon, 1 Elunium (both awarded randomly by opening treasure chests), 5 Blue Gemstones, 5 Red Gemstones and 5 Yellow Gemstones (all dropped by the Fake Angel on "Geffenia" and "The Endless Tower" maps). Alternatively, these items can be purchased from fellow users in Prontera.
Enter "War of Emperium."
Go to the broken Guardian Stone and place the Stones, Elunium and Oridecon down in that order.
Wait for the Guardian Stone to project a colored aura and place the gemstone of corresponding color down. For example, if the aura is red, use a Red Gemstone.
Repeat six more times to finish rebuilding the Guardian Stone.