I've made myself a PayPal account for this and another online MMO, because 1) this game doesn't have anything like cash cards, and 2) I don't feel like walking through thirty minutes of freezing cold for cash cards for the other one. Imagine my frustration when it takes 3 days for PayPal to verify my bank account, and another 8 to get the $50 to buy energy with. So I finally got it today...
...And PayPal tells me it will take another 10 days to complete the payment.
I'm sorry, Three Rings, but I have to protest. Spiral Knights is a game where if you need energy, you need it right away. I have to wait almost three weeks for mine, just to pay off all the energy I owe other people because I haven't had any myself.
Frankly, I feel insulted that Three Rings only has Credit Card support. What about us less-fortunate people who only have debit accounts? I'm getting tired of waiting. Please, add support for debit transactions.
Three Rings cards do exist and I know they're sold at Target (not sure where else), but they don't include Spiral Knights yet. Once the game is released, I imagine SK will be included.
In the meantime, check out the official wiki page on billing inquiries. There are other payment methods available for people who don't own credit cards. You can purchase energy with cash (USD only), money order, or check. There's also something called PaidByCash, but I'm not entirely sure what that is.