But you can cheat to get passed that with a nice trick! Change the date! It's that simple. Make yourself 24 hours ahead. This works on consoles and PC. You can likely get a trainer to hack your saved data or game, but I wouldn't. There may be a patch soon that will fix this.
For the below one, no real glitch needed for this secret!
Xbox 360 How to Farm Seraph Crystals Borderlands 2
It works on Xbox 360. Be careful with it though!
You can just farm crystals all day long if you wish. Once you're done, go to the Seraph Vendor at Oasis to buy Seraph weapons, Seraph shields, or Seraph relics / Artifacts.
Compared to a lot of rare, epic, and legendary loot, these Seraph gear aren't overly impressive. Some are very powerful though! Seraph items are labeled with pink text and many people would trade for them on XBL / Xbox Live.
PlayStation 3 Keep ALL Seraph Crystals Borderlands 2
You can do a similar technique to keep Seraph Crystals so that when you buy something with them, you keep all your crystals. Check out the video below.
Lastly, here's another example of a mod / glitch where Hyperius the Invincible is being killed over and over again in a party.
I hope you like getting Seraph Crystals Fast! Enjoy and share your tips if you have any suggestions.