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The Propeller Cat is both a pet and an interactable NPC. The Propeller Cat is awarded for reaching wave 25 of Sky City on either Survival and Pure Strategy mode.


The pet multiplies the attack damage of heroes, functioning like an Apprentice Guardian for heroes rather than towers:

  • The Boost Intensity stat (the blue arrow) determines how strong the damage multiplier is. The formula for calculating this is ( 1.1 + ( (Boost/20) ^0.835 ) * 0.145 ). Example increases are shown in the table below:
Boost Intensity Damage Multiplier


75 1.5372
100 1.6559
125 1.7698
150 1.8799
175 1.9870
179 2.0039
200 2.0917
224 2.1900
  • This multiplier directly stacks with the Monk's Hero Boost ability.
  • Boost Intensity can be upgraded on every 3rd level, so level 3, 6, 9 and so on.
  • Boost Intensity can spawn at a maximum of 140. As the greatest level Propeller Cats can reach is 254, Boost Intensity cannot exceed 224, or 221 if Additional Heroes are upgraded fully.
  • Additional Heroes is the number of other player characters the pet can boost. It includes the player wearing the cat.
  • Additional Heroes always starts at +1, so initially only the player wearing the cat receives the boost. It can be upgraded every 30th level, so 30, 60 and so on.
  • Additional Heroes has an upgrade cap of +4, for a total of four players. This was the maximum number of players any mission could have when the Propeller Cat was released, as this was before maps that allowed 6 heroes.
  • Range is the distance at which other players can receive the boost from the pet, provided Additional Heroes is at least 2. If there are more heroes in range than the pet can boost, it prioritises the closest players (starting with the player wearing the cat which is always considered to be range 0).
  • Range can be upgraded every 5th level, so level 5, 10, 15 and so on.
  • Range can spawn with a maximum of 90, which is also its upgrade cap. 90 is roughly the distance between the pet-attackable tavern dummy and the Forge.
  • Due to the upgrade timing, every 15th level presents a choice between Boost Intensity and Range (unless the latter is capped), and every 30th level presents a choice between all three pet stats (unless Range and Heroes are capped).



Skycity NPC Locations
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