On each opponents upkeep that player loses a life and you put a -1/-1 counter on a creature they control
Cards like Mind Twist, Time Walk, and Demonic Tutor ride a fine line with the metric of taking it pack three regardless of your deck, but they are a good reason to pick up black and blue dual lands and Signets that touch your main colors in the first two packs
As a note, all the information above holds for 40 of the 41 legendary creatures in the set
He'll show you how marked cards can act as a failsafe in case your trick goes wrong
One of those is that this green, white, blue and black 4/4 has Flying, Vigilance, Deathtouch and Lifelink - but its mostly the other ability
Their Name Is Death is an absurd board wipe for a deck is almost entirely made up of artifact creatures