if Thirteen is Untapped, tap Thirteen and block all damage dealt that turn, thirteen is then put into graveyard and can be returned if its controller pays {X}, where {X} is the number of creatures on your battlefield

Every time an opponent attacks, if Thirteen is untapped, tap thirteen and all damage dealt that turn is blocked.

Flying, (This creature can't be blocked except by creatures with flying or reach.)

when attacked, equipped creature may roll a D20, if 10 or above, they dont take damage