"Largely inspired by jmizzle7's description of how he imagined this card, the Amethyst Tower is supposed to be a large, nonsensical structure, through which entropical energy flows in seemingly random patterns. Fun fact: the background of this tower was originally going to be the background for the Bone 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.