What does it mean to "Challenge the Character"?
Combat is a perfect example really. Very few of us know how to use a halberd. None of us can cast a fireball. But, our characters can. How they do it? Dunno. Don't particularly care either. But, I do know that they can. So, when combat ensues, I'm not expected to tell the group how I hold my halberd or how I wave my hands and make a fireball shoot out.
Sure, the decision to use a halberd or a fireball is a player decision, but, the solution to the problem of the orc standing between you and the pie is found with the character, not within your ability to figure out how to stab that orc.
Once upon a time, adventures were designed to be very, very player facing. Tome of Horrors is probably the best example of this, but, there are others. Solving the Tomb of Horrors is a challenge to the player because, really, it doesn't matter terribly much what kind of character you bring in. None of the challenges, or at least very few, are character facing.
Contrast that with, say, Caves of Chaos. The characters you bring will very, very much determine your ability to achieve goals within the caves as my very first group of characters, 5 1st level MU's, discovered to their folly, falling foul to a fiendish flock of stirges.
ncG1vNJzZmivp6x7prrWqKmlnF6kv6h706GpnpmUqHy4tMCtZJ2nlah6qsCMppyapl2pvG6vx5qjpZ2enLJuwMeeZJygkaeupMDEq2VvbWhtgnV7