Terraria is Steam’s most-beloved game, and for good reason. It blends elements of classic action games with the freedom of sandbox-style creativity, all of this available to experience in various difficulty modes!
With various difficulty modes come different events and phenomena, one such phenomenon being the phrase “The air is getting colder around you…”. This status message has to do with one of the exclusive Hardmode bosses of Terraria, Skeletron Prime.
Skeletron Prime is a Hardmode mechanical boss which is, at its essence, a more difficult version of Skeletron. It consists of a head and four limbs, but similarly to Skeletron, only the head needs to be beaten to defeat the boss.
Skeletron Prime can be summoned manually using a Mechanical Skull at night (7:30 PM to 4:30 AM), while also having a 1/10 (10%) chance to spawn naturally at dusk once a Demon or Crimson Altar has been destroyed, as long as it has not been defeated yet at least once in the current world. If spawning this way, its arrival is announced by the status message “The air is getting colder around you…”.
If Skeletron Prime is not defeated by dawn, it will start behaving much like a Dungeon Guardian, ceasing to use its limbs and charge at the player at extremely high speeds instead, dealing usually lethal damage upon contact.
According to the official lore of the game, Skeletron Prime was one of the three mechanical recreations of Cthulhu’s missing organs, while being a recreation of part of Cthulhu’s skeleton.