The four-cost uncommon will counter and then they'll discard too
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)
This is a great mana sink when you dont have other plays to make, but if players cannot make the most of The Earth Crystals activated ability, then the Crystal is not worth playing
The common Lesson cards aren't included here as they are in the Lesson slot above
Imagine playing Cristophe, bringing back Flickerwisp, and Blinking Cristophe to bring back another creature
You are trying to pressure your opponent and force them to react, allowing you to draw three cards and pull even further into the lead