Cerberus' medallion, Aspect of Agility, is the only one to give you a new power instead of a buff. Once you kill Cerberus at Grim Gate (look for, and interact with, a pedestal that has his statue ...

The Super Shield Medallion creates a Shield Bubble Jr. around the player when they are healing themselves. This ability will not activate if players use Slurp Barrels, Gold Splash, or Med-Mist ...

To gain Underworld Dash, you can either spend some time bathing in the green water bodies around The Underworld and Grim Gate or holding onto Cerberus’ Aspect of Agility medallion.