The Beast, Deathless Prince 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

When you cast this spell, gain control of target creature until end of turn. Untap it. It gains menace and haste until end of turn. The Beast enters tapped with six stun counters on it. (If it would become untapped, remove a stun counter from it instead.) Whenever a creature deals combat damage to its owner, untap The Beast and draw a card.