Prophecies are quests. Completing prophecies sometimes offer rewards, such as items or upgrades. To see the current and completed prophecies speak to (click) the prophet at your base.
Reignite the Seal
When you have 3 Essence of Rage, double click the Burned Out Seal (while in your inventory) to receive the Burning Seal and complete the quest.
(Note: You will lose the essence and burned out seal.)
Essence of Rage are dropped from all bosses in Burning Cave and Chamber of the Sealer.
Burned Out Seal is dropped from Magadom in Chamber of the Sealer.
You are able to make multiple burning seals, however, as it's unique, you can only equip one at a time.
Once you have 3 essence of rage, they will no longer be dropped.
Find the dwarfen runesmith!
On farm level 23, look for the Dwarfen Runesmith (he will look different than everything else on the level) and click him to complete the quest.
You do not have to complete level 23.
Build the Beast Slayer
All the items are dropped by the bosses in Frozen Coast.
The schematics and warox hide are dropped by the oxes, wolfman bones are dropped by the wolves and the lizard sinew is dropped by the lizards.
Once you have the schematics and the materials, go to the Runesmith's Shop and "buy" it to complete the quest and get the beast slayer.