How the super moves work in the Viking game. Taking damage or dealing it fills up your meter (the blue circle around the character icon) until it reaches the top and starts glowing. Tapping it starts up a drawing minigame- if the player traces it accurately enough, they unleash the super move, which is based on the weapon the character has equipped. Although super moves do massive amounts of damage, they aren't a guaranteed finisher nor are they impossible to dodge.
EDIT: Updated interface with more elaborate drawing symbol to look fancier.