Each hero has six core stats: HP (Health Points), Atk (Attack), Spd (Speed), Def (Defense), Res (Resistance), and Lck (Luck, though not directly displayed, it influences some skills). When a hero is summoned, they receive a random 'IV' (Individual Value) spread, meaning one stat will be slightly higher (+3) and one slightly lower (-3) than their neutral base stats. For example, a +Atk/-Res hero will have higher Attack and lower Resistance. Understanding IVs helps you determine a hero's optimal role and build. You can check a hero's IVs using various online tools or by comparing their stats to neutral values.
