It is the defining card of several top-tier competitive archetypes
People say its a ramp spell and a speed bump, because opponents are less likely to attack into it and give you a card, or worse, trade with it
Domain Ramp All of the colours Domain Ramp is named so because of the Domain keyword, which has an effect on cards based on the number of different basic land types you control, and ramping, which is where you put extra lands into play
Pull the thread down the centre of the signature and out (again) through the bottom hole, to the outside of the books spine
Id also never go below four copies of Darksteel Citadel because it plays a big role in some of your nut draws
Occasionally I play it because it discards mine but mostly I play it to draw me seven cards for three mana