Four

Four is the primary host of Season 4, Battle for BFDI. Four has very absurd mannerisms, like being able to deform characters, revive them, and screech in order to stun characters. Four's first appearance in BFDI is Getting Teardrop to Talk, where they lead a game to win "a BFDI" (in which it means the winners will get another battle for Dream Island). Four appeared alongside X, another abstract being representing a real-life number or variable. Although Four seems calm most of the time, he appears angry in BFB 2 for a few times. Cary Huang has suggested that he and X are some sort of extra-terrestrial being.

Coverage
Four's first appearance was in a 2008 animation by Jacknjellify called X Finds Out His Value along with X, where he helps X figure out his value by factoring out an equation.

Nine years later, Four and X appear in BFB as the hosts. Unlike his original appearance, he acts extremely odd and screeches at others who try to talk to him, making them faint, become dizzy, or even die (in the case of Pillow). The only two characters who can actually communicate with him are Dora and Roboty, who also only talks in a strange manner. As of now, it is unknown if he can understand X.

Trivia

 * He appears to have four fingers on each hand, however, when he is grabbing Black Hole before the intro, he has five.
 * He appeared in the HTwins.net game Tidepool, as a level 23 creature in the "Classic" character set.
 * Cary described Four as a "weird alien creature who doesn't know how to communicate" in his reaction video. If he actually is an alien, this could explain his strange powers, general behavioral quirks, and different eye and limb assets.
 * He explains challenges in a way where the problem is shown (performed by X, sometimes himself) and he instructs the objects to the task as a challenge.
 * Four seems to be omnipotent. However, being omnipotent doesn't grant him the ability to give good solutions to the problems which he is faced with all of the time.
 * He has the ability to recover and kill contestants, replacing the Recovery Centers for this season.
 * He can also transport eliminated contestants to an unknown place by sucking them into himself, replacing the Tiny Loser Chamber and Locker of Losers for this season.
 * Four might represent the show's fourth season, although there's no clue of what would happen to him in season 5.
 * Four accidentally calls the team A Better Name Than That "Another Name Than That" in BFB 2, a running gag in the BFDI series whenever Golf Ball can't think up a team name.
 * Four and X have terribly animated mouths sometimes.
 * Four was originally a darker shade of blue.