Siphoned Energy is a resource that can be acquired by doing Guild vs Guild related activities, such as taking over castles, claiming and holding territories or raiding other guilds territories and killing their siphoning mages.
Siphoned Energy can be converted into runes, souls and relics at the artifact foundry in Caerleon. Current energy conversion rates are:
i.e. 1 energy is required to produce 1 T4 relic, or 6 energy is required to produce 1 T6 relic.