Maze, as a highly adept user of Will, has these markings on his body. The Hero of Oakvale also can get them on his own body as he increases in the amount of spells he has at his disposal and their power level.
Scythe, as an ancient Hero himself who has mastered the ways of Will, has these markings on his body.
When the Hero of Bowerstone becomes skilled in Will spells, dim blue lines, or veins, will appear on his or her skin. The more experience with Will, the brighter these become. Eventually, the will lines turn the Hero of Bowerstone's eyes blue, even if the Hero is evil or corrupt. There is no way to remove these lines except discarding spells. Garth, "Hero of Will", also has these markings due to his extensive expertise in Will.
Tattoos act as will lines and they can be red if the Hero of Brightwall is evil. Additional Will lines appear when he or she uses Will, flourishes, or charged gun attacks on whatever clothing he or she is wearing, the colour of which is based on the Hero's moral alignment. When charging up for a Flourish or magic, those Will lines will appear instead of the tattoo lines unless the tattoo can be viewed outside of the clothing (ex: chest tattoo for females).