Each character has four pieces of gear that can be upgraded to increase their damage, defense, critical hit rate and other attributes. This requires gold and items that are dropped during missions. When you have the proper ingredients to complete an upgrade, a small dot will appear on the "Gear" button in a character's profile. Skills are the easiest thing to improve, simply by spending gold. The two starting skills can be leveled at the same rate as the character's level. Always try to improve them after leveling up. Other skills will become available as you rank up that character. You can master your heroes by using various Norn Stones. This is similar to ranking up, except the stat improvements are greater. This will also improve their leadership ability.