Here's what each ring can do...
Triton Ring: You can survive underwater even longer than a whale (You still need to breathe), as well endure crushing pressures and freezing temperatures (Which improves your physique to peak state). Also, aquatic animals will identify you as one of their own and won't attack unless you directly harm them.
Empusa Ring: Your body becomes healthier, stronger and more attractive, allowing you to ''charm'' most people with your soothing voice. Also, by drinking the blood of other creatures, you can heal any wound or ailment you suffer from (Including growing back lost limbs in the course of a few months), as well stagnate your aging with enough blood. However, destroying your heart, behading you and any extreme damage like those cannot be healed from.
Dryad Ring: You can manipulate plant life and make it grow strong and fertile. With this ring, you can sense the earth's ''purity'' and know where crops will surely grow and eventually, learn to purify a limited patch of land from any polution.
Nemean Ring: You gain enhanced strength and superhuman resilience (Including bulletproof skin), becoming Earth's physically strongest human. Not only your senses of sight and smell are improved too (You now have night vision), but all felines will respect you and will not attack unless provoked. While your recovery speed is faster than the regular, you cannot regrow lost body parts or instantly heal from ailments like the user of the Empusa Ring.
As expected, you cannot use the ring's power without wearing it. However, if you wear a ring for an entire year without ever taking it off, you'll gain its powers for good.
Triton Ring
Empusa Ring
Dryad Ring
Nemean Ring
