3rd Aug, 2017By Softmints9 minutes

Keys of Sealing is a rare example of an AoS whose gameplay is formally divided into stages: imposing a structured path to victory rather than the blurred lines of "early-game", "mid-game", and "late-game". It also has a special victory condition that is more teamfight-oriented than the familiar "destroy the main base".

In this review I'm going to cover features from both early and later versions together, as there aren't too many differences.

Overhead view of terrain
We don't see an air lane very often! It activates later into the game.

The Book of Sealing:

Keys of Sealing's most distinctive feature is it's unusual victory condition. Instead of a main base that needs to be destroyed, the game gives a cinematic introduction to the Book of Sealing which is located near the center of the battlefield.

This Book is protected behind a layer of barriers, and three keys must be used to remove the barriers. Once exposed, having a hero channel for 2 minutes in front of the book (without dying) bestows victory.

The book, behind glimmering walls of light.
The Book of Sealing, currently behind barriers.

Thus, the game is divided into three stages, of no fixed length:

  1. Securing the keys needed to control when the book will be exposed
  2. Securing an advantage to expose the book at a favourable time
  3. Fighting to control the area around the book for 2 minutes

The First Stage

Each team starts with one key in their base's vault. This is a 'sanctuary' space: protected on all sides and barred by a gate. It's not impenetrable, but at least one lane of barracks needs to fall before swiping a key becomes practical.

Outside the vault and occupying a central position in the base is the team's goalie hero, an NPC tasked with guarding the entrance to the vault. It spawns at the start of the game, and levels up over time to acquire spells and stats. If it dies, it will revive after a short delay at the nearby Altar, ready to fight some more.

Picture of a hero beside a building in its base
The goalie hero at his altar, with a few stationary troops to defend.

That's two keys accounted for. The third is held by a boss called the Spirit of Destruction; located near the center of the map, and who must be slain before his key can be claimed. The Spirit is quite powerful and has an army of lackeys with him, though neither those nor the Spirit will respawn after death: so whittling his forces down over time is an option.

Accompanying the Spirit are two Magic Vaults which contain loot, but take time to break open (and are only vulnerable after his death). This means that a team who gets the key can still be denied of the accompanying loot if the area is actively contested.

A powerful demon on a throne, surrounded by minions
In earlier versions, the Spirit enjoyed a private chamber underground; teleporter access only.

The keys are individual items which must be brought to the Book of Sealing to dismantle its barrier. Once presented, a key's purpose is fulfilled and it vanishes. This can be done one-by-one, but the barrier won't drop until all three have been consumed.

Until then, they are items whose location is known to both teams at all times. They will drop if the hero carrying them dies, and each key also provides a passive bonus to the hero who holds it: splash damage, frost attack, or purging attacks depending on the key.

Thus, a hero can remove the key from their own vault right away and use it for a combat advantage... though generally this isn't a good idea until later in the game, or at the point where the vault is no longer secure.

An NPC called the Keyseeker roams randomly across the map, and actively snatches up any keys that are left unattended for too long outside a team's vault. If this happens, he must be hunted down and killed to reclaim the stolen keys, though he respawns immediately to continue his task.

Even when none of the three keys are in his possession, the Keyseeker still has a purpose: he drops a special item called Heart of the Obelisk which guides the bearer to an otherwise inaccessible secret shop. It strikes me as thoughtful to have integrated the Keyseeker mechanic with some other parts of the map: it would have been so easy not to. Secret shops are no longer in vogue, but this is great flavour for a map of Keys of Sealing's era.

To wrap up: the first stage of the game has a good rhythm. There are incentives to push down lanes, to grow stronger as quickly as possible, and as vaults become less safe: lots of encouragement to hunt enemy heroes and try sneak the boss.

The Second Stage

Once a team is in a controlling position with keys, they have the option to try and build an advantage before dropping the barrier, at which point either team will have an equal shot at contesting the Book of Sealing.

There's lots of ways to build an advantage that can be converted to a (hopefully) decisive victory... though no promises on anything going smoothly! Of course, building an advantage can happen during the first stage as well. Let's examine some of the options.


There are two capturable towns on the map, which will spawn extra troops for whichever team owns them. A town is captured by destroying a modestly durable building in the center of the town; the other buildings are invulnerable and simply produce troops. Any 2-3 heroes who show up and focus the building are sure to succeed in taking it.

Once captured, the building will respawn for its new owners at about 20% maxlife, so it's still very contestable if the capturing team isn't committed. The 'town' building has regeneration (it will heal to full in 100 seconds), so it can endure unfocused fire, and returns to being a bit harder to contest if a recapture isn't attempted immediately.

The towns differ in value; the 'strong' town to the west produces good troops and will hold itself indefinitely; the 'weak' town in the east will hold, but can sometimes flip back and forth without hero intervention. Having both towns under your control is a great springboard for victory.

A building shoots fire at nearby enemy troops
The strong town's Supply Depot is... a throne packing a flamethrower. Who knew?


Of course, the best thing about capturing towns is they make pushing easier, and in Keys of Sealing losing a barracks means losing troop production on that lane. Thus, it's possible for the second stage to extend for a while if a team feels they can force the enemy into a permanent lane disadvantage, before dropping the barriers.

Once that happens, the game will be focused around the Book of Sealing, and allocating time for counter-pushing becomes more difficult.

There are still options though: players can hire mercenary units, including siege specialists that can quickly recapture a town and provide a foothold on that lane. The other mercenaries are a building-repair unit, basic ranged attackers, a caster, and a big tanky unit. Their restock time is quite long, so building up an army would have to start early.

Another option for getting a troop advantage is paying for some of the troop upgrades available in the Altar, which follow the usual trend of +damage/+armour with high cost, and long cooldowns on each upgrade. I've written about this implementation for troop upgrades before, and I'm not a fan (though they're less impactful here than in other maps).

Gold Income:

Close to each team's base is their gold mine; sporting a long line of busy workers running back and forth harvesting. Despite appearances, they have no impact on player income at all, but can still be raided to pick up some last-hit gold (if you have AoE damage; otherwise they're cumbersome to clear out).

A hero gains gold from killing a line of worms waddling to and fro from a gold mine
Clearing out the enemy worms, for a profit.

What does have an impact on a player's income is their wages! Every in-game day, heroes are paid by their faction based on their performance so far. The formula gives more gold to higher level heroes, more again for total player/unit kills, and subtracts for each death. (For this reason, gold mine workers can be used as a slightly more efficient way to inflate unit kills and increase a player's wages.)

The idea's cute, though this system hugely rewards early kills with both experience (that leads to levelling and higher wages faster) and a kill which will pay dividends for the rest of the game. Similarly, each death causes a small but permanent reduction in wages.

In games where losing gold on death is a mechanic, wages (or generally, deferring rewards) can help balance situations where two heroes kill each-other, but one hero benefits more because they died first (losing little to no gold) and then got a kill (awarding bounty), while the other gets a kill first but then loses that bounty with their death. Generally, "dying first" isn't supposed to be a good thing, and waiting before paying out means that the death/kill is what counts, not the order in which it happened.

While they're nice for flavour, neither of these gold mechanics contributes to overall gameplay. Numerically, neither system offers anything better than the gold for last-hitting troops and heroes, so their existence is largely a flavourful one.


Keys of Sealing has many quests around the map, taking the form "fetch this item for me to get a reward". They often involve fighting hostile monsters. Most quests can only be completed once, so players might end up racing or interrupting each-other's quests if they know the map well and feel the rewards are worthwhile.

Much of the game is framed in terms of quests: collecting the keys is technically the main quest. The second most important quest, which these days would be called a map objective, is killing the enemy's reserve hero. This is a max-level NPC hero camped outside each team's base, usually stacked with strong items and auras. The hero will sit in place, waiting patiently for two possible outcomes:

  1. To be killed once by the enemy players, and laid to rest for all time.
  2. For the barrier on the Book of Sealing to fall, at which point reserve heroes gain the ability to revive when killed. As we'll soon see, this turns out to be a big deal.
A paladin hero waits off-lane in the forest, and has several auras visibly active
Sitting in reserve for now, but those auras will make a difference later.

Finally, I'll mention that there's creep camps scattered all over the map so farming these is also an option for building an advantage (en-route to quests or otherwise). However, their returns aren't great.

The Third Stage

The keys are assembled, the barrier falls, and the victory condition of "a hero channels in front of the book for 2 minutes without dying" becomes open to all takers. But as the stakes get higher, the factions up their game as well:

  1. A new lane opens up: air units will start flying directly to the Book of Sealing at the center of the map to contest it.
  2. The goalie hero and reserve hero will leave their posts, and fight their way to the book to channel on behalf of their team.

This definitely raises the level of excitement! The air lane has some spawning rules: the troops stand guard at the book instead of continuing to the enemy base, and troops won't spawn if there's already a wave on guard. (This seems fair.)

Frost Wyrms and Gargoyles attack a hero, which is channeling in a marked area
Trying to channel, but the enemy air superiority won't let that succeed.

The second point, about NPC heroes being willing to channel, is a critical saving grace for the game. If a human player was forced to sit and channel, I would be very unhappy about it.

Instead, NPC heroes can do it (but they have to be escorted to the book along the mid lane, as they'll try to pick fights along the way). Players can still volunteer to channel themselves, and that might be strategically the right choice in some cases.

With this in mind, the reserve heroes are clearly a big deal. The extra max-level hero with all those auras; and willing to channel the book even when your goalie hero is occupied fighting off the west lane? Very helpful. If you have key control in stage two, taking out the enemy reserve hero is a top priority. That said, teams still have their goalie hero no matter what.

The air units can get distracted by enemy troops in their base, so if the mid or left lanes have lost their barracks and no-one's holding them off, that can impact how many fliers make it to the center. Thus, even though taking barracks doesn't lead to taking a main base, it still contributes an advantage in the third stage.

I think this works out as a pretty exciting victory condition in cases where there's an even fight. In an uneven fight where one team has complete map control (two towns, reserve hero advantage, upgrades, possibly up a barracks...), it may be too hard to contest and turn things around. Well, put those wages to use and don't fall behind!

Heroes and the Safe Zone

It's not so clear from the map, but the team bases in Keys of Sealing don't have any fountains for friendly heroes to heal at. This is because heroes revive, heal, and shop in a separate dimension from the main battlefield, which I'll call the safe zone.

To leave the safe zone, players step onto a teleport pad matching their preferred lane (or the base), and are instantly teleported to the appropriate exit point. There are separate exit points for each team. All exit points can be used by either team as re-entry points, and re-entry requires a short channel.

A fountain in a walled-off room, with several spaces marked as teleporters
The safe zone, with pads for each lane and a separate one for the base

It's nice to be able to revive and immediately jump back to your lane of choice, and once the game reaches the third stage, having a reliable central access point is great.

For general get-around purposes, there are also waygates in the corners of the map which connect opposite corners. There are 30 heroes available for each team. They're customised for flavour, and later versions have a couple of triggered spells.

The items for sale are weak compared to other games, though the numbers all-round are low enough that +6 to a stat feels like it makes a difference. In general, heroes will be leaning on their abilities more than their item builds.


One of the things I like about Keys of Sealing is that it recycles mechanics from the first two stages (the goalie heroes, taking barracks, and the keyseeker) and keeps them relevant during the third stage. That aspect of the design feels really clean to me.

I also like that the lanes have a clear hierarchy: the strong town is the most important and will push the fastest, the weak town is useful and contestable, and the mid lane is hardest to push with, but gains importance over time as the boss becomes viable to fight, and controlling it allows NPC heroes to reach the book. The addition of a fourth lane in the final stages is a nice touch.

If the economic system were tightened up in a few areas (consolidate last-hits and such into wages, drop exploration quests for a central shop, give gold mines a clearer purpose), I think the game would have felt really sharp and been suitable for competitive play and development.

The lesson from Keys of Sealing is that alternative victory conditions are a rich space to explore, and having the 'form' of the game evolve with new lanes and objectives is an area with lots of under-appreciated potential.