Cheapest priced copy (Mirrodin): $1.79 at Card Kingdom, near mint, their price list as of .
Tangleroot 
Artifact · Rare · Mirrodin · #259
Whenever a player casts a creature spell, that player adds {G}.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
1 printing · $1.79 to $6.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Mirrodin | 259 | Rare | $1.79 | $6.99 |
One ruling from Wizards of the Coast
- 25 January 2011The player gets the mana whether they want it or not. If it isn’t spent, it will disappear at the end of the current step (or phase).