The public quests will begin and run through their entirety on their own, whether or not any players are currently participating. Even with a public quest in progress you can enter the region and join in. Public quests will always begin at the same time every day instead of at random times (ex: 1:30pm, 2:30pm, etc). Depending on how long the previously run PQ took, the next public quest may have either a very short or very long time before it begins.
A public quest progresses through several stages as it continuously runs. They are dynamic, meaning that the content will scale up or down in difficulty depending on how many players are actively participating in the PQ and whether the stages were successes or failures. The mobs in PQs are non-contested. This means that they cannot be locked, that you cannot kill steal and that you can jump in and assist an ungrouped player with a mob they're working on.
As mentioned above, a public quest will scale in difficulty. These quests can scale from solo to a x4 raid! This is determined in a variety of ways. First, a large number of players present at the beginning of a public quest will cause the original stage to be more difficult. Difficulty can also increase during a public quest if players begin to clear stages too quickly. Alternatively, the quest can restart a failed stage (including stages where the time runs out) with lower difficulty if the players present cannot handle it.
A few other NPCs play fun roles in public quests, such as a runner that may deliver supplies that you can utilize in battle or pet-like battlers that will happily engage the enemy at your command.
Since encounters are not locked during a public quests, players can invite others to groups and raids at any point. This will benefit everyone participating in that you can be a more cohesive force when you band together; however, it is not required to participate. An AFK player in a group or raid will likely not get participation credit solely because the rest of their comrades are contributing, so it is important to still take part in the quest!
The more difficult a public quest is, the better the loot in these treasure chests will be! Armor is not a guaranteed reward but, depending on the difficulty of the PQ, there is always a chance of it being in the chest, though it is not as frequent at higher difficulties. The armor will range from items that are akin to overland quest rewards (solo difficulty) through fabled rare drops or red slot adornments (hardest raid difficulty).  There are also alternate reward choices aside from armor pieces, which vary by difficulty and the public quest.
According to Windslasher on the EQ2 forums, this is how the loot breaks down:
Within each difficulty there's a common and a rare version of the cache -- the rare one has "Exquisite" in its name. Their rarity varies a bit but is never lower than 25%. At difficulty 1-3, only the exquisite cache contains an armor piece, while difficulties 4-5 always drop armor for everyone (but the exquisite drop is better). The overall quality of the drops and your number of choices also goes up with difficulty.
For known Great Divide PQ rewards, see below.
At the end of each public quest, participants will see green shinies around the quest region! There is one collection for each PQ, and the shinies are first come, first served among contributors.
In Game Update 64 a public quest in Antonica was added. It is called Frenzy of the Mange and is a level 20 PQ. Higher levels can mentor down to 20 to be able to participate in this quest. Rewards are appropriate for the level of the quest regardless of what the player's actual level is.
In Game Update 62 a public quest in The Commonlands was added. It is called The Cleansing of the Bonepile and is a level 20 PQ. Higher levels can mentor down to 20 to be able to participate in this quest. Rewards are appropriate for the level of the quest regardless of what the player's actual level is.
There are currently two public quests available in the Great Divide.
To participate in the Echoes of the Ring War quest, head to the Ring War Battlefield around 258,-330,-409 in the Great Divide. This quest runs at odd hours: 1, 3, 5, 7 (Pacific Time).
To participate in The Battle of Storm Gorge quest, head to the great wall of Storm Gorge around 531,380,1157 in the Great Divide. This quest runs at even hours: noon, 2, 4, 6, etc (Pacific Time).
NOTE: Participating in this public quest will not negatively affect your Order of Rime faction. The mobs required for this quest have no detrimental faction associated to them.
Rewards are highly varied upon difficulty of the public quest and chance. The more difficult the PQ ends at, the better the rewards, but also the lesser chance you have of receiving and armor piece compared to the easier tiers. You can only choose one reward from all the options you are given. See Reward Chests above for a more thorough explanation.
Each public quest will reward one Cloudy Velium Jewel per day. It will be automatically added into your currency window when you loot the reward chest. This item is used to sell to faction merchants in Velious to raise your faction by 500 with them.
|Thrumming Cache||Exquisite Thrumming Cache|
|Minor Transmuter's Stone||Small Transmuter's Cache|
|Orb of Advancements||Greater Orb of Advancements|
|Sacred Ring (250 Favor)||Sacred Ring (374 Favor)|
|No fourth reward choice.||a Prevalent Armor Piece|
|Resonating Cache||Exquisite Resonating Cache|
|Small Transmuter's Cache||Transmuter's Cache|
|Prevalent Orb of Advancements||Greater Prevalent Orb of Advancements|
|Sacred Ring (500 Favor)||Sacred Ring (625 Favor)|
|Transmuter's Stone||a Prevalent Armor Piece|
|Reverberating Cache||Exquisite Reverberating Cache|
|Transmuter's Cache||Greater Transmuter's Cache|
|Victorious Orb of Advancements||Greater Victorious Orb of Advancements|
|Sacred Ring (750 Favor)||Sacred Ring (875 Favor)|
|No fourth reward choice.||Greater Transmuter's Stone|
|No fifth reward choice.||a Victorious Armor Piece|
|Pulsating Cache||Exquisite Pulsating Cache|
|Greater Transmuter's Cache||Transmuter's Hoard|
|Triumphant Orb of Advancements||Greater Triumphant Orb of Advancements|
|Sacred Ring (1000 Favor)||Sacred Ring (1250 Favor)|
|Greater Transmuter's Stone||a Triumphant Armor Piece|
|a Victorious Armor Piece||No fifth reward choice.|
|Humming Cache||Exquisite Humming Cache|
|Transmuter's Hoard||Greater Transmuter's Hoard|
|Dominant Orb of Advancements||Greater Dominant Orb of Advancements|
|Sacred Ring (1505 Favor)||Sacred Ring (2000 Favor)|
|a Victorious Armor Piece||a Triumphant Armor Piece|
|Any one of the following is a possible ultra-rare reward choice.|
|a Dominant Chest Piece||a Dominant Weapon|
|Red Adornments (need info)|
|February 22, 2011|