The Dej-Wah is a "spiritual weapon" used by Delvians. It is first described in the Farscape comic issue "Talkin' Kkore Blues" before being used to defeat the Kkore in "The Peace to End All Wars."
Completing the Dej-Wah requires multiple Delvians coming together in prayer. Zhaan attempted to harness the Dej-Wah when assassinating Bitaal, but her decision to do it alone shattered her mind.
When the Kkore invade the galaxy, Scorpius suggests using the Dej-Wah to defeat them. However, because of Bitaal, there are not enough strong-minded Delvians for it to work. John Crichton realizes that anyone of any faith can contribute to the Dej-Wah.
With Stark channeling the Eidelons' power and the combined prayers of all the Resistance members, the Dej-Wah is successful. It empowers the Resistance, and they finally see the path to victory.