Why do you need the chaos emeralds in sonic?

* To go along with the actual storyline, the Chaos Emeralds will give ultimate power to whoever possesses them. Sonic just needs to make sure that Dr. Eggman doesn't get his hands on them. * Concerning the actual gameplay, Sonic 1, if you collect them all, you unlock the true ending. In Sonic 2, Sonic 3, and the Sonic & Knuckles series, if you collect all the Chaos Emeralds, grab 50 rings and jump, you'll transform into Super Sonic! A alternative ending will also be available.