The "first challenge"

Jack blinked, and found himself standing in a forest clearing surrounded on all sides by a high, sweeping canopy of trees. A faint breeze was stirring the leaves, and various kinds of birds tweeted and flitted amongst the branches. A collection of various kinds of wildflowers grew all around Jack's feet.

"It's....PERFECT," Jack thought, looking around him. After a moment, he noticed a small gap in the trees across the clearing from him, and a faint trail worn into the ground that led from the clearing through the gap and into the shade of the forest canopy ahead, where he lost sight of it. He knew the beginning of an adventure when he saw one. He lifted his newly-obtained magical axe to his shoulder, and trudged off into the woods, attempting and failing to whistle the theme song to one of his favorite television series as he entered.

The trail led straight for a couple hundred feet through the forest floor, picking its away around various large trees and stones, and across a small creek about five feet wide that bisected it. Here and there, small forest animals such as rabbits and squirrels climbed and jumped and darted around the floor and trees, some of them gibbering in protest and running to their hollows as he interrupted their tasks.

A short way past the creek, the forest began to thin, and the trail began to ascend a steep hill. Following the switchbacks up the hillside took more effort than Jack was used to exerting, and he instinctively braced himself for the breathless exhaustion he was accustomed to when he did much more than cook instant ramen. To his surprise, however, none came. He felt just as rested and energized at the top of the hill as he did at the bottom. So this was what not being an out of shape piece of shit felt like. Jack let out a sigh of relief. This. was. AWESOME!

["YOU LIKE YOUR NEW BODY, KID!?"]

Jack screamed, fell on his ass, and nearly tumbled down the hill as Frumpkin's voice exploded inside his head.

"AAAuuggh! GOD!", Jack yelled, flinching and rubbing his ass. He looked around himself, but saw nothing but trees, hillside, and one particularly perturbed looking squirrel, who was chattering at him angrily from a nearby branch.

["YES?!"] Frumpkin yelled inside his head.

"STOP YELLING! YOU'RE HURTING MY HEAD!", Jack said, curling into a ball and clutching his skull like that would actually do anything.

["OH JEEZ! SORRY KID!"]

Jack heard the sound of rustling, and a few clicks like someone was flipping switches and pushing buttons inside his head.

["...This better?"] Frumpkin asked.

"Yes. Christ." Jack said, starting to stand.

["My bad. Last kid who tried this route was deaf as a doornail. Forgot I still had the sensitivity turned all the way up. Also, I'm in your head. You don't have to respond out loud for me to hear you. Just think it, and I'll hear it."]

"Then you can hear this, then?", Jack thought to himself.

["Yep. ...You could try and sound a little less sarcastic."]

"Sorry. Just still trying to get used to all of this," Jack thought.

["I'm sure. Now, what do you want to unlock as a reward first? Item, skill, or companion?"]

"Wait, what? Already? But I haven't even done anything heroic yet!" Jack thought. Even he found getting upgrades this early completely ridiculous.

["Yeah, sure you have. The hill was your first challenge. You're still fat. You overcame it. Now, do you want a set of magical plate armor, lockpicking skills, or a familiar?"]