Hotel of Fears is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

At the beginning of your upkeep, exile the top card of your library. You lose life equal to its mana value. You may play that card this turn. Praise Him — Whenever chaos ensues, choose a color. Put X +1/+1 counters on target creature you control, where X is your devotion to that color. Then sacrifice another creature. (Your devotion to a color is the number of mana symbols of that color in the mana costs of permanents you control.)