Random Generator gave me Fire-Lit Thicket and Compulsion. My first thought was to give the line:

­, Discard a card from your hand: Add to your mana pool.

But even if that line of text was fair, it wouldn't be very fun. And I'm not even sure if that line of text is fair... It doesn't matter how much it hurts if it lets you win the game...

So I figured out this compromise. By the time you've charged this up to add two mana to your pool, two turns have passed, and two cards discarded. You can go to three or four if you want... but that's a lot of waiting around and cards discarded. You want that sort of continuous stream of mana, though, go for it. I don't know... maybe you're packing Mind Springs. That sounds pretty good. Meanwhile, you don't feel too bad throwing away those resources, since you're just looting them very slowly... or late game winning with a pile of mana I suppose. I'd like to see the player who gets this up to , just to throw a twenty point Fireball.

Wow. Interesting. Reminds me a little of... Vexing Sphinx, maybe? I think that probably is fair, given that it starts at 0. I really like the ability to pop it to reclaim the cards you put into it.

My only concern is whether it's a little good with proliferate. But then, lots of things are. From the proliferate point of view, this is like a combination of Everflowing Chalice which did the incremental mana thing, and Culling Dais for the cards.

I think your first idea would be simultaneously irritating and overpowered, so well avoided.