Spectral Knights are spectral warriors that appear in the Curse of Castle Blackburn mini-campaign in the Steam, iOS, and Android versions of Kingdom Rush. They are one of the three enemies in the series that are completely immune to physical damage, the others being Ghosts and Phantom Warriors
Tormented souls of oath breaking knights doomed to roam between life and death.
Spectral Knights either spawn from entrances as a normal enemy, or from a Fallen Knight when they are killed (in that case, they give no gold when killed). Either way, a humming sound will be heard for each one that appears on the battlefield. They are essentially Phantom Warriors who traded HP, death aura, and damage for the ability to boost Fallen Knights around them, adding 4 minimum and 15 maximum damage. In contrast with their 90% magic resistance when still alive, necessitating the use of archers and artillery; after rising from the dead, they become completely immune to physical damage of any kind, making mages absolutely vital to stop them, because heroes will be overwhelmed by their numbers. The Spectral Knights' physical immunity and the Fallen Knights' high magic resistance make a very powerful and annoying combo when they spawn together.
- Sorcerer Mages are very good at killing them, using the curse for extra damage and earth elemental to stall them longer.
- Paladins will block them for a long time, and can harm them with Holy Strike.
- Arcane Wizards are very effective with their high magical DPS, while Teleport and Death Ray are both very useful against them.
- Although Oni is a melee hero, both of his special abilities are capable of harming them.
- Gerald Lightseeker can use Shield of Retribution to reflect damage and harm the spectral knights.
- Elora Wintersong deals high magic damage, making her perfect to kill them. With the support of barracks or reinforcements holding the Spectral Knights off, she will kill them in seconds, not even necessitating mage towers.
- Even though Spectral knights don't receive damage from soldiers and call reinforcements, the Spiked Armor that is upgraded can harm Spectral Knights.
- Hacksaw's Flying Sawblade and TiiiImber work against them, although he can't do anything else other than stall them.
- Rain of Fire does harm them, but don't waste rain of fire because Spectral knights don't really had that much health compared to most other enemies. Use it when there are 4+ Spectral Knights and there are about to escape.
- It is suggested to upgrade the mage tower into Arcane Wizard, because low-level mage doesn't really deal high damage to Spectral Knights and the range is pretty short.