"The tower isn't the structure itself. It is all of us, and the wisdom we share. It grows ever upward, a stone for every new arrival."
—Archmage Vintra
If multiple effects modify your hand size, apply them in timestamp order. For example, if you put Null Profusion (an enchantment that says your maximum hand size is two) onto the battlefield and then put Reliquary Tower onto the battlefield, you'll have no maximum hand size. However, if those permanents enter in the opposite order, your maximum hand size would be two.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.