Whimsun is encountered in the Ruins, usually shortly after meeting Toaddit.
Unlike Undertale, Whimsun is quite harsh and often harasses the player during the fight. It often makes fun of and calls names at the player.
Whimsun summons several dark-red flies from the side of the screen which fly through the fightbox, dealing 4 damage if touched. Whimsun can also attack the player directly by throwing itself into the fightbox.
Whimsun appears to be in a dark shade of orange, with an angered expession, equipped with sharp, jagged teeth. The wings allow the sprite to constantly fly up and down.
The player can flee the battle. However, one can also beat Whimsun by fighting, or by attempting to console. If the player attempts to console Whimsun 3 times, it grows bored and leaves the player.
Whimsun first encounters the player at the beginning of the room after the long hallway, where it gets in the player's way and attempts to bully them.
The player will find Whimsun hanging out next to Toriel's house if spared correctly. It will tell the player to "Go Away" if spoken to.