Based on context, there's a chance the term "challenge" is a less confrontational version of battling or attacking an enemy card
cheap evasive dork, high CMC relative to real cost of playing, a ninja, an EtB effect, and/or disruption
You can get the only foil version surprisingly cheap, but it wont be cheap for long
6) Pikachu 279/XY-P XY-P Promotional Cards (2016) US$32,520 The fourth and finaland most expensivecard on this list honoring the Pokmon TCGs 20th anniversary was Creatures Inc.s magnum opus as far as cards related to the milestone are concerned
Collective Brutality The life drain on Collective Brutality might be the least picked mode, often just tagged onto the Duress or -2/-2 so you can discard a reanimation target, but thats a pretty decent effect
Professional Protection: GRAAD's sealed capsule provides optimum protection against external factors, maintaining its value