As long as Thunderstaff is untapped, if a creature would deal combat damage to you, prevent 1 of that damage. , : Attacking creatures get +1/+0 until end of turn.
If Thunderstaff is untapped, it prevents 1 damage from each creature, each time it would deal combat damage to you. So if three creatures with double strike attack you and aren’t blocked, Thunderstaff will prevent a total of 6 damage.
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.