Classic-Mu has new Ring/Pendant system
In order to upgrade your rings, you need to have all type of excellent rings or pendants, and make them +4 HP Recovery with
Jewel of HP Rec You can get this jewel from Green Ribbon Box 
and events that drop custom jewels [like Medusa or White Wizard]
Pendant options:
- Increase attack speed +30
- Automatic HP +4%
- Increase Ignore damage rate +3%
- Damage increase +4%
Rings options:
- Increase HP +4%
- Automatic HP +4%
- Increase double damage rate +2%
- Damage decrease +4%
Combinations:
When you have 2 same ring and pendant combination, following options will open:
Glory - Increase HP +5%
DarkAngel - Increase defense +5%
Holy - Increase double damage rate +5%
Blue - Increase damage +5%
Soul - Increase excellent damage rate +11%**
