Their only ability lets you exile a card from your graveyard to discover for X, with X equalling the mana value of that card
It is a bit strange that it has an ETB trigger, though it does make it a bit more consistent, if less value in the long term
Therefore, you can't actually use the land for mana for a couple turns after you play it, rendering the mana accelerant fairly ineffective for competitive play
Lightning Greaves Rarity: Uncommon TYPE: Artifact SUBTYPE: Equipment CMC: 2 Mana cost: USD: $7.25 EUR: 4.01 TIX: 0.03 EDHREC RANK: 13 Equipped creature has haste and shroud
The lands are Snow mainly for Coldsteel Heart, board wipe Dead of Winter and Iceberg Cancrix
I mean, sureyou get the occasional Cleric that's awesome, but as a general rule, they are small, they prevent damage of some sort or another, and they are boring