From Guild Wars 2 Wiki
Resonance was a guild resource.
- Bring a Shard of Crystallized Resonance (a random additional reward from guild missions) to resonance technician Peejj at your guild workshop, who will turn it into 100 resonance for your guild (see Refined Resonance).
- Buying 100 resonance directly from that same NPC for 25 4 (see Resonance Requisition Form).
Unlike what was original planned, resonance cannot be obtained by grouping with other guild members.
- ^ "After internal testing (...), we've decided it isn't necessary to incentivize guild members to party up.", Guild Mission Changes and Improvements