If I have access to the best mana rocks for my Commander deck, I should usually prioritize those over any situational ramp spells, but use my best judgment when comparing them against my best mana ramp options
The Taxes elements come from creatures like Thalia, Guardian of Thraben and Mother of Runes, making all your opponents spells cost one more and effectively turning off single target removal spells by giving creatures protection from a color of your choice
All you need is a free CGC account to submit, but paid members receive discounts on certification services
Overall, if you are looking to play a Dark World deck, I strongly recommend to start from 2 or, better, 3 copies of the structure deck to fuel more cards to your strategy and to remove those that weaken it
Yellow Border - WOTC Style - Cosmos Holo image19203212 985 KB I have heard rumors these Filler Cards originated from WOTC employees
I have no doubt it would be put to nefarious uses in modern where you can suitably build around it