Rainbow cards belong to no king. They come from the Jack of Rainbows, they can land in any run, and several of them ignore limits that every other card obeys.
What a Rainbow card is
Each of the nine kings owns 9 to 13 cards. The Jack of Rainbows owns 32, more than any two kings together, and none of them start in anybody's deck. That makes them the one part of a run you cannot plan around and the part most likely to change it.
They are not stronger copies of king cards. Most do something no king card does: move by themselves, level a plot past its cap, copy a whole plot, or turn one building's effect into nine. A Rainbow card is worth the most when it lands on an engine that is already running.
The Jack also has 9 perks of his own and 15 decrees. The decrees appear in the Royal Council like any other and many of them are about getting more Rainbow cards.
Every way to get one
The merchant is the source you can put a date on. Every card slot in a merchant's store has a 2% chance to be a special card, and the merchants come in years 7, 19 and 31. The Lucky perk makes Rainbow cards 20% more likely in shops. The Rare Goods decree skips the odds: every merchant shop always sells one Rainbow card.
The rest are cards and decrees that convert something you have. A Gacha triggers a Rainbow loot event when it reaches max level. Diffract destroys a plot and gives two random Rainbow cards. Refraction replaces your whole hand with random Rainbow cards, and Relics turns every treasure chest into a Rainbow chest.
| Source | When | What you get |
|---|---|---|
| Merchant | Years 7, 19 and 31 | 2% chance per card slot |
| Rare Goods (decree) | Every merchant after it | One Rainbow card always on sale |
| Gacha (building) | On reaching max level | A Rainbow loot event |
| Diffract (tome) | When played | Two random Rainbow cards for one plot |
| Refraction (decree) | When picked | Your hand becomes Rainbow cards |
| Relics (decree) | After it | Every chest is a Rainbow chest |
Rainbow troops
Six troops, and each has a rule instead of raw stats. The Dwarf moves to an adjacent plot every year and gains 50% to all stats when that plot is locked. The Ogre gains 5% to all stats a year for every empty plot beside it, so it wants to stand alone at the edge. The Replicator adds 9 units to itself every year with no help. The Slime copies itself onto one empty adjacent plot each year, which fills a kingdom fast and is only good if you wanted those plots filled.
The Golem is the one built for combos: any tome used on it has double effect. A Migration on a Golem is worth two, and so is a Procreate. The Scapegoat does not fight at all. It grazes in the backline and pays 3 gold a level if it is killed in battle.
None of them levels like a carry. An Ogre gains only x1.1 HP and attack per level, and a Scapegoat gains nothing but units. Their rule is the whole card. Give them the board position the rule asks for and spend your buffs elsewhere.
Rainbow buildings and the Obelisk
The Warehouse is the one to hope for. Effects of the other buildings beside it are applied one more time per level, so a level 3 Warehouse next to a Blacksmith, a Forest or a Recycler makes each of them work four times over. Place it where it touches the most support buildings, not next to troops.
The Shrine spends 9 gold a year to level up one random plot, and costs 3 less per level. The Temple adds 9% to a random stat of a random plot. Both are slow and unaimed, which makes them better in a small kingdom where the random plot is often the one you care about. The Codex gives back a copy of any tome used on it and then destroys itself, one more copy per level: use it to double the single best tome in your hand.
The Obelisk is the only Rainbow tower. Its damage rises by 900% every time you lose a life. With three lives that is at most two triggers before the run ends, so it is a comeback card and a poor first pick.
Rainbow tomes and spells
This is where the limits get broken. Patronage levels your base plot by 3 and works beyond its max level. X-Ray levels every plot diagonal to its target beyond max level, so aim it at the centre of four plots you care about. Echoform duplicates a plot and all of its stats onto an empty neighbour, which makes it worth more every year you wait to play it.
Balance sets a plot's HP and damage to whichever is higher. On a Paladin plot, where damage buffs have been raising HP all run, it turns the tank into the killer. Gigantify doubles a troop's size, damage and HP. Osmosis gives +30% to all stats to every plot of the same card as its target, so it rewards a kingdom that repeats one card. Surge triggers a support building's effect 9 times at once: on a Recycler, a Camp or a Blacksmith that is nine years of its work in one card.
Several are trades. Extraction destroys a plot for 5 copies of its card. Unify sacrifices every troop beside the target and adds their unit counts to it. Randomfy turns a plot into another card of the same type and doubles its current stats, a gamble that is only safe on a plot you were going to replace. Razing destroys a plot forever and calls a Royal Council on the spot.
The Rainbow spells are small. Precision adds first hit damage per stack, and Smite fires a laser at a random enemy when its bearer is hit. Mantra, the newest, gives its bearer +3% to all stats per stack every time any plot levels up, so it grows fastest in a kingdom that levels often. Take them for a Wizard, which gains 5% damage for every enchantment it bears.
The Jack of Rainbows' perks and decrees
His perks rearrange the perk grid. Authoritarian makes the top left regular perk count three times, Moderate makes every universal perk count twice, Leftist and Verticalist repeat the perks next to them, and Nationalist does it for every adjacent king perk. Expander adds 2 slots to a row and Seasoned gives 30% more experience. Lunatic is the odd one: taken as your only perk, it starts the run at war with the Jack of Rainbows himself.
Among the decrees, Longtermism lets you choose 3 decrees at the next Royal Council and Multiculturalism calls a council of decrees that belong to the other kings. Magic Bricks lets towers carry enchantments and hands you 3 that fit, drawn from Adrenaline, Combustion, Freeze, Mantra, Midas Touch, Static and Venom. Mantra can turn up in a run through it. Wishing Well gives 3 copies of the next card you throw into the pit. Invisibility stops ranged troops taking damage, at the price that they no longer block enemies, so it needs a melee line or a wall in front.
The Jack brings his own army in year 17 and again in year 27 of every single player run. Both dates are fixed, so have the kingdom ready for a fight that is not the king you have been facing all run. The King of Nothing has a reason to look forward to both: his Benevolent perk gives a Wildcard after every Rainbow army battle, and a Wildcard is a level on any plot.
Mistakes to avoid
Dropping the engine for the new card. A Rainbow card bought in year 19 has fourteen years left. Add it to what is already working.
Playing Echoform, Balance or Surge early. All three scale with what the target already has.
Letting a Slime loose in a planned kingdom. It takes an empty adjacent plot every year, including the one you were saving.
Buying a Shrine with no income. It needs 9 gold every year, which is a whole year's base income at level 1.