Colossus (Colossi ?) invariably show up on every exploration level that is a multiple of 30.
Colossus are fought much like you fight the Monster Islands and Player's airships. You can assault them directly or go through the details page to see their stats and fight with the help of an Exploration Runestone if you so wish.
If you own Hovering and your Energy is high enough relative to the Colossus energy, you can also get an instant victory by choosing the Destroy option.
Besides spending a Runestone, other things can be helpful specifically against Colossus:
- Various Celestial Titles
Colossus will drop Relic Fragments, Mysterious Statues and can drop Airship fragments and most importantly the Energy Crystals needed to upgrade your Sky Medals and build Gumball Statues. See Energy Crystal to see which Crystal can be found at which level
Various effects can increase the rewards:
- Elemental Continent Halo : Sky EP + -/-/15/20/25/?% when attacking Sky Colossus
- Elemental Torrent, Magic Cannon from Elemental Continent: 10/20/30/40/50/? Sky EP after you win the Sky Colossus battle
- Medal of Scholar in your Ancient Mining Pit : Crystal drop chance +10%/../50%