Mox Amber
Oracle Text
: Add one mana of any color among legendary creatures and planeswalkers you control.
Card Rulings
4/27/2018 Mox Amber’s ability adds one mana of the color of your choice from among the colors of legendary creatures and planeswalkers you control. It doesn’t add one mana of each of those colors.
4/27/2018 If you control no legendary creatures or planeswalkers, you can activate Mox Amber’s ability, but you won’t add any mana.
4/27/2018 If your legendary creatures and planeswalkers are all colorless, you can activate Mox Amber’s ability, but you won’t add any mana. Colorless is not a color.
This one seems unplayable, unless you have a bunch of 1-drop legendary creatures. Isamaru? I dunno. Otherwise it's ramp that comes too late in the game.
Who knows, I don't pretend to understand pre-release prices any more...or the prices of cards in standard for that matter