Think of this as a day-0 pick order for FDNs best uncommons
That being said, however, a new Eldrazi Commander deck that arrived alongside Commander Masters did feature the powerful ability
4 Titania, Protector Of Argoth Futureshifted Frame - $221.12 An incredibly powerful legendary creature from Dominarias ancient history, Titania, Protector of Argoth has popped up a few times in Magics modern history, with this iteration being particularly strong
I know many of you love these cards
The way challenging works is a ready (untapped) character exerts and chooses an opposing exerted character to challenge, and then both cards compare their strength (attack) and willpower (defense) values to each other (meaning the attacker automatically gets hit back by the defender)
A tapped creature is very unlikely to be damaged by anything, so this looks very close to a 1-mana Claustrophobia