"Zaborg the Thunder Monarch" has a mandatory effect that occurs when it is Tribute Summoned successfully. You have to destroy 1 monster on the field. This is normally a great effect, allowing you to destroy 1 of your opponent's monsters. But if the opponent has no monsters when you Tribute Summon this card, you have still have to destroy 1 monster, and that means it has to be a monster you control. Controlling no other monsters will not help, because if there are no other monsters, "Zaborg the Thunder Monarch" will have to destroy himself. Make sure to read all your cards thoroughly before using them, so you do not activate a mandatory effect that will hurt your own strategy.