Originally posted by Myrolit Studios:

Strength (sword symbol): Increases your damage and gives you a chance to stun the target.
Toughness (shield symbol): Reduces damage taken and the duration of stun effects.
Agility (winged shoe symbol): Increases your movement speed and gives you a chance to evade attacks.
Dexterity (crosshair symbol): Gives you a chance to critical strike (double damage) and heals you for a small amount of your caused damage (lifedrain).
Serenity (cross symbol): Increases all healing received and regenerates a small amount of health over time.