Untaidake having so many restrictions is indicative of how careful R&D can be when creating lands which produce multiple mana, though its an example of a card so thoroughly underpowered, that its essentially unplayabale outside of EDH and the Legendary Cube
Llanowar Elves has recently sold out of every copy under $700, so while it had a dip at one point, the trend is clear and its not like anyone is mass-cracking Foundations at this point
This can make you the de facto inevitability baron and make every long game basically approach impossible for the opponent
For instance, the Final Fantasy crossover includes double-faced cards to represent iconic characters, minigames, and story moments
Whenever an opponent discards a land card, add to your mana pool
Though somewhat costly at six mana, this simple yet stellar green enchantment states that each of its owner's lands may be tapped in order to produce a treasure token