I am a bit confused of the artifact card Terrarion. Does this card allow me to gain 2 mana of any color forever when I tap 2 mana, tap Terrarion, and sacrifice it? Or do I only gain that mana for that turn?
What Terrarion basically does, is repaint the color of mana. If you have two blue mana, but need a red and a green one, you can activate Terrarion's ability.
Let's look at that ability: The cost to activate it are on the left side of the
:, and he effects on the right. The costs are:
pay 2 mana, tap Terrarion and sacrifice it.
- The mana may be of any color, or even colorless
Why bother tapping it if we're going to sacrifice it anyway? Terrarion comes into play tapped, and once it's tapped you can't tap it again. So, in the first turn you can't activate this ability.
Sactifice it. This one's obvious. Note that Terrarion has a
leaves the battlefieldtriggered ability, so you get to draw a card.
As for the effect: You can choose to add 2 mana of any color (though not colorless - Terrarion requires us to choose from the Colors of Magic: Red, Green, White, Black or Blue). They can be two different colors, or 2 mana of the same color, as per Gatherer:
You can get either two mana of the same color or one mana each of different colors.
But didn't we just pay two mana. Yes, we've paid 2 mana of color XY, and gained 2 mana of color WZ. You have effectively repainted 2 mana to better suit your purposes.
It sounds like you are confused between lands and mana. Lands are cards that (usually) produce mana; they are "permanents" so they stick around on the battlefield turn after turn. Mana is always a temporary resource (usually obtained by tapping a land, but also available from other sources like Terrarion) which you either spend to cast spells and such, or don't spend in which case it vanishes at the end of the current phase of the turn. There is no such thing as "gaining mana forever".