There are several shared quests to keep track of during each game. Completing these quests provide important benefits for all your team. You can find the requirement for each of these quests in the F9 section of the game.
Completed by sending Pack Horse challenge (Coral Bed) enough times.
Rewards Gold Coins item.
Completed by killing Revenant of the Seas (Necropolis) enough times.
Rewards Spiked Collar item and 1 food.
Completed by having enough tier 3 towers in the game.
Rewards one tower improvement.
(Firelord doesn’t count as a tier 3 tower for that quest)
Completed by upgrading enough tier 1 towers to lvl 5.
Rewards one random ancient orb.
Completed by buying enough tier 2 items (Altar of the Depths).
Opens the Forgotten Storage system that allows players to effectively trade items by selling them to the ship.
Completed by using exchanging gold enough times (Galaxy Bank).
Unlocks the Wand skill ability on the builder that allows players to trade tier 2 or tier 3 towers available from secret tower or dragon keys.
Also increases all players wood income by 1.
Completed by killing dragons (Coral bed) enough times.
Rewards an Empty Vial.
Completed by summoning 1 revenant of the Tides and 1 revenant of the Depths (Necropolis).
Unlocks the ability to upgrade the Tidal Guardian into one of four Hero Altars.
Completed by selling one lvl 5 tier 2 tower.
Rewards an ankh item.
Completed by increasing the Neutral chance to 20% (Tidal Guardian).
Rewards one Neutral building that lets the player build any neutral tower, even neutral tier 3 tower if they were unlocked prior to placing the Neutral building.
These quests can only be completed once per game and are not repeatable.
The requirements for shared quests scale off the number of players in the game.