it's a cool idea but i don't think you need to make it an uncommon; it's a worse Stone Rain. you can use it for self-fixing i guess but that doesn't really justify the bump

It's uncommon because of complexity. It is a strictly worse Stone Rain, though a lot of things are - I'm pretty sure WotC doesn't / can't print LD at 3cmc anymore.

this feels like a low bar for complex but whatever floats your boat

Not comprehension complexity, strategic complexity. It doesn't ramp, so it's not obvious what it's for. It's not useful in all situations. Not a card I want a totally new player to see often.

I feel like land destruction is baselined at 4 casting cost now just to give decks breathing room. But Wizards still seems to think of Stone Rain as costing . Otherwise Demolish and Volcanic Upheaval would cost more. They didn't really increase the cost of LD... they just refuse to print cheaper LD spells.

With this spell, however, you aren't doing anything a Sea's Claim couldn't do. Granted, this is better (not vulnerable to Naturalize for one thing) but I get the impression that is fair enough.

On a side note: If the Mountain doesn't enter the battlefield tapped, you can use this to give an ally a bonus mana for a turn. Whether that's cool or not is up to you.

Holy crap, you're right. Thus is a really bad Spreading Seas

Previously:

­ instant
Search your library for a Mountain card and put it onto the battlefield under target player's control. If you do, destroy target land that player controls.

Now it's basically a Harrow that targets.

What's your deck do?

Replaces all my opponent's lands with twice as many wastes.

It's a better Cultivate if you have Darksteel Citadel or Terra Eternal, but no one plays the latter :^)

Re: Terra Eternal - Alex has a deck of nothing but animated lands to go beat the opponent with; it'd fit in there :)