Greenpois0n RC5 now allows you to jailbreak iOS 4.2.1 untethered on most devices including iPhone 4 and iPad. The best part? You won't need any SHSH blobs saved. redsn0w beta required you to have 4.2b3 blobs saved (and it was pretty unstable). Hopefully greenpois0n is going to be a much smoother experience for you guys. Hit the jump for a walkthrough on how to jailbreak iOS 4.2.1 with greenpois0n and for the answers to some commonly asked questions.