You start with the King of Nothing and nothing else. The other eight kings each sit behind one counter, and the Joker sits behind all of them.
The nine conditions
Every king's unlock is a single count of something ordinary: cards used, gold spent, units killed. The sizes are very different. Nine spells fit inside a single run. 999 years is the length of more than thirty full runs, because a run to victory lasts 33 years. The game gives each condition and says nothing about how it is counted, so the scale column takes a count to keep what earlier runs added, whichever king played them.
The table is sorted by how much play each one takes, lightest first. That is also the order worth chasing them in, for a reason beyond speed: the early kings bring the cards that make the later counts go faster.
| King | Unlock condition | Scale |
|---|---|---|
 King of Nothing | Unlocked from the start | None |
 King of Spells | Use 9 spells | One or two runs |
 King of Nomads | Use 99 troop cards | A handful of runs |
 King of Stone | Build 99 buildings | A handful of runs |
 King of Greed | Spend 999 gold | Several runs |
 King of Progress | Level up 299 plots | Several runs |
 King of Nature | Train 999 units | Several runs |
 King of Blood | Kill 9999 enemy units in battle | Many runs |
 King of Time | Play for 999 years | Thirty runs or more |
 Joker | Unlock all other kings | Last by definition |
Spells, Nomads and Stone: the quick three
The King of Nothing's own deck covers all three. Steel Coat is his spell, so nine of them played is the King of Spells. Soldier, Archer and Paladin are his troop cards, and every copy you play counts toward the 99 for the King of Nomads, whether it opens a new plot or stacks on an old one. Farm and Blacksmith are his buildings, and each one put down counts toward the King of Stone's 99.
The habit to drop is throwing spare cards into the pit. While these three counters are open, a spare Soldier played onto the Soldier plot is progress, and a spare Farm is too.
Stone is the slowest of the three because a kingdom has few plots and a building takes one. Unlocking plots early is what speeds it up, since every new plot is room for one more building.
Greed, Progress and Nature: the middle three
Spending 999 gold sounds large until you count what a run offers. Base income is 9 gold a year. A new plot costs 30. A merchant's first card costs 30 and each one after costs 15 more, and rerolls start at 10 and rise by 10. Three merchants visit in a run, in years 7, 19 and 31. Arrive at each with gold and leave with none, and a run spends nearly everything it earns.
Levelling 299 plots is about replaying cards. Each time a card lands on its own plot again, that is one level, and most cards stop at level 3. The King of Nothing's Wildcard levels any plot. Once the King of Stone is yours, his Earthworks returns up to 3 copies of a plot's cards to your hand, and playing them back down is three more levels.
Training 999 units favours cards that come in big groups. A Soldier or an Archer card is 9 units at a time where a Paladin card is 3, and a Farm adds a unit a year per level to a troop beside it. If the King of Blood's Imp turns up as loot, it is 13 units a card.
Blood: 9999 kills
This one is counted in enemy units, so it depends on how many arrive. Enemy armies are bought with a troop budget that grows with the square of the year. It is 13 points in year 1 on every difficulty and 1197 points in year 33 on Peasant. About two thirds of a run's enemy budget arrives in its last ten years, and a run that dies in year 15 has barely added to the count.
Which king you fight matters as much. Armies made of cheap troops are bigger: at the year 33 Peasant budget, a King of Greed army is about 160 units and a King of Progress army is about 443. Declaring war on swarm kings and winning through year 33 is the fastest route, and playing on into endless mode keeps the budget climbing.
Higher difficulties add to the budget too, but only if you still reach the late years. A finished Peasant run beats a failed King run for this counter every time.
Time: 999 years
No trick shortens this. A won run is 33 years, so the King of Time is roughly thirty complete runs, or fewer if you keep playing a strong kingdom deep into endless mode. He will be the last of the nine for almost everyone.
Treat it as the counter that fills while you do everything else. Unlocking the other seven, levelling kings and clearing difficulties all add years. The one way to waste it is abandoning runs early: a run dropped in year 6 because the start was poor gave six years where finishing it would have given 33.
The Joker, and what else unlocks along the way
The Joker opens when all nine kings are unlocked. For now his deck is three cards, Soldier, Paladin and Archer, the same troops the King of Nothing starts with.
Other parts of the game open on their own schedule. Quest Mode unlocks after you beat one run. Multiplayer unlocks after three games, and you can only bring kings you have unlocked in single player, which is one more reason not to stop at four or five. Beating the game on King difficulty unlocks the option to reroll your starting enemies.
Perks are separate from all of this. Each king earns his own by levelling up, so a newly unlocked king starts from level 1 no matter how long the others have been played.
Difficulties are shared between kings. The game keeps one unlock per difficulty, not one per king, so a level opened with the King of Spells is open for the King of Blood as well. Climb with the king you play best and bring the others up afterwards. Higher levels also pay more experience: every difficulty has its own multiplier, x1.3 on Peasant, x4 on King and x7 on King IX IX.
Mistakes that slow it down
Restarting until the opening hand is perfect. Years played are a counter, kills are a counter, and both only move in runs that go long.
Pitting duplicate troops and buildings while Nomads and Stone are still locked.
Hoarding gold through the last merchant in year 31. Gold left over at the end of a run counted for nothing.
Jumping difficulty to speed up Blood. More enemies arrive only in the years you survive to see.