MTG Salvation

The name and flavor are works in progress, but heres the mechanic:

Wash (As you play this, you may return any number of lands you control to their owner's hands. Each land returned in this way reduces the cost to play this by 1 or by one mana of any color that land could produce.)

An Example:

Aquamaro- 5UU
Creature- Elemental
Wash
This has power and toughness equal to the number of cards in your hand.
*/*

Now, the mechanic is obviously broken if it isn't priced correctly. Also, its broken if attached to certain cards. Armageddon would be broken with this. Its also broken with card draw.
Any suggestions?

Well, Wash effectively cuts a card's cost in half, cause you can tap your lands for mana, then bounce 'em for an undercosted spell. Balancing this by making everything cost twice as much kind of defeats the purpose of the mechanic. It also has crazy synergy with armageddon, as you said. Plus, with cards that let you play extra lands or put lands in your hand into play, you can accumulate a huge amount of mana in your pool. A suggestion is that you could do Wash # (As you play this, you may return up to # lands you control to their owner's hands. Each land returned in this way reduces the cost to play this by or by one mana of any color that land could produce.) This let's you regulate how many lands you return per spell, preventing any really abusive combos. Not sure what they would be right now though.

Actually, I don't think small effects are all that bad with Wash. You may be playing the spell for free but you are also damaging your tempo in the long run. This isn't much of a price for a big finisher but you probably aren't going to want to sacrifice the tempo for a quick answer to a threat. Now, as long as the card's effect can't compensate for the tempo loss, there isn't much need to raise the mana cost. Even with effects that give you card advantage or tempo, playing the spell for free will probably cost you more tempo than you gained. The bigger the effect though, the higher this ability needs to cost though. At least thats what I think.

What do you guys think?

Quote from Belgareth »

Or just allow return of untapped lands thus making it more a penalty cost as opposed to broken.

Then wouldn't you almost always tap the land instead of returning it? This makes the mechanic useful to about 2 decktypes.