1. Cerulescent bell. In West Willow (thanks to Dragonlady).
2. Lutescent bell. In thieves_arcadia map under Port Kuudad's sewers.
3. Virescent Bell. Lorewitch tower. Floor 2.
4. Rubescent Bell. Hammerlorne. Level 2.
When you collect all 4 bells go to Port Kuudad to library. There will be locked gate there. Library's owner, Saint Gihelm, will unlock the gate if to show him orakur book, which was collected in bronze easter egg (search in forum for this). Gihelm will open even more ancient library. Step there and find something similar to umm... firtree? Anyways, click it and
