"This has got to be the favorite pillar art I've made for the game. The dead marsh, the bone pile, the sense of dread and eerieness.. It comes together so well on this card. For Death, I don't think I could've made a more suiting tower." -vrt
Pillars are the staple of basic quanta generation in game; they are free to play (they require no quanta to place onto the field), and are considered to be the practical backbone of almost every deck in game.
Because of the requirements to play the various creatures, spells, and non-pillar/pendulum permanents in-game, pillars (and their upgraded form, towers) are essential for any player to generate a steady flow of quanta. Also, pillars are one of the few single-card permanents to create a stack upon being played (pendulums being the other permanent to stack on cards similar to itself). While this saves space on the permanent field, certain cards (Earthquake) can demolish the stacks of pillars very quickly as a form of quanta denial, so one should be careful about how and/or when they play these free cards when fighting certain opponents.