I like the idea, but this seems exceedingly strong land acceleration for red. The fact that it doesn't use up a land drop makes it better than Thawing Glaciers in some situations.

Or Mountain for that matter. Even without the second ability, this card is better than a basic mountain, since it gives you a free shuffle.

I made it so hat the mountain comes out tapped, and increased the cost to recur it. Does that make it more acceptable, or should I have it recur to hand instead of the battlefield?

Hmm, there's a turns delay on using it the next time; and you have to already be at four mana. It doesn't seem like it would break anything this way.

I got away with Redmine which is a lot faster than this.

The key difference between Redmine and this is that Redmine put the land into your hand. (Vitenka got away with Redmine on the basis of one or two drafts: it was good but not absurd, and there were bigger things to fix ;) )

It's certainly possible to nerf this hard enough that it isn't any good. But I wonder if a different kind of tuning might be better.

I wanted it to be flavorful red mana acceleration. I wonder if that's possible without it being busted.

I don't know. It seems too close to call for me. There's a point where the activation isn't worth it, but I guess it would require testing to figure out where that is. At least you had the good sense of doing it during the upkeep, as opposed to letting players activate this at end of the opponent's turn. That probably would have been too good at 5...