Guild Wars 2 – Help Paenula train the troops by fighting in the pit

“Capture minotaurs and drakes for the fighting pit using Paenula's rifle, and spar with beasts in the fighting pit.”

Head to the Southwest of the Extermintus HQ. Just to the East of the path you will find Paenula Drakecatcher. Talk with her to get more details on the renown quest she is offering:
Paenula Drakecatcher: “Welcome to Ashford Forum, where soldiers fight the fiercest enemies they're likely to face on the battlefield. Are you here because of the help wanted sign?”
Hero A) “No. But if you need any –“ B) “I'm here because someone mentioned rifles!”
Paenula A) “Great! Our inventory's a little low on drakes and minotaurs, so you could go bag a few of those alive. Plus, we could use someone of your ability to help out by training soldiers in the pit.”
Hero C) “What is the Pit?” B) “How do you capture these creatures alive?” D) “What do you mean,  “training soldiers in the pit?”
Paenula C) “Just host to the finest battlefield simulations in Tyria. Small groups can go toe-to-toe with drakes, minotaurs … even Separatists, when we have them in stock.”
Hero D) “Why have battle simulations?” B) “How do you capture these creatures alive?”
Paenula D) “It's all the fun of real battle, without all the messy glory. Soldiers find out how they'll fare against the enemy in controlled environment. Better to die here, now, than on the battlefield later.”
Hero F) What do I have to do?” Hero B) “How do you capture these practice enemies alive?”
Paenula F) “The pit's right at the top of that ramp. We've got a few soldiers already waiting for the next battle. Just tell Bracctus on the second level what you're in the mood to kill.”
Paenula B) “I've created cruelty-free rifles that makes it easy to capture 'em unharmed. So if you wanna go bag a few in the wild, take one of these rifles. Just stun 'em, then net 'em. I'll do the rest.”
Hero E) “Why not? Always willing to try out new weapons.”
Paenula E) “Here you go. You should find a whole mess of the critters just southeast of here. Good luck, good hunting, and don't forget – that rifle's a loaner.”

Rifle Skills
Bleeding Shot: “Fire a shot that bleeds your target.”
Range:1,200, Damage: 14, Bleeding (6s): 47 Damage, Combo Finisher: Physical Projectile (20% chance)
Blunderbuss “Bleed foes with a shrapnel cone shot that works better the closer you are.”
Range: 400, Damage: 50, Cooldown: 5s
Within 8 feet: Bleeding x4 (12s): 348 Damage
Within 16 feet: Bleeding x3 (12s): 261 Damage
Within 24 feet: Bleeding x2 (12s): 174 Damage
Within 32 feet: Bleeding x1 (12s): 87 Damage
Rifle Butt “Knock your foe back with your rifle butt”
Range: 130, Damage: 27, Knockback: 450, Cooldown: 7s
Net Shot “Immobilize foes with a net shot, capturing those under 50% health.”
Range: 1,000, Immobilize (3s): Unable to move
Jump Shot “Aim downwards and blast off the ground to fly at a foe known you both down.”
Range: 1,000, Leap Damage: 59, Landing Damage: 59, Blast Radius (10s), Combo Finisher: Leap, Cooldown: 20s

If you want to just fight, head to the left of Paenula Drakecatcher. There you will find Bracctus. Just stand in the arena and wait for the next fight to start. You have a variety of options of scaling difficulty.
Drake (easy), Minotuar (Medium), Separatist (Medium or Hard) Minotaur (Hard). Here you just need to stand in the pit and win the fights. It only takes a fight, maybe 2, to complete the quest.

Following the conversation along the lines of the rifle will get you one. That means you will want to head to the Southeast, toward Lake Adorea's Eastern side. There you will find an abundance of minotaurs. Head more toward the lake and you will find a lot of Salamander Drakes. Once any of the minotaurs or drakes are at or below 50% health is when you want to fire the net. You can easily finish off this quest here with this alone.

This is not a hard quest to complete. Once it is done you will get the letter, “Thanks for Your Assistance” with 71 copper:
“Hello,

“I just wanted to thank you for your help with the arena. The soldiers need training to keep their skills sharp, and they've gotten their fill fighting the minotaurs and drakes you captured. Well done – Paenula Drakecatcher”

Return to Paenula Drakecatcher and she will be selling the following Karma Items:
Iron Harvesting Sickle: 49 Karma
Used to gather taproots, spinach, strawberries, herb sprouts and all other lesser edible plants. Can also crack open clams. Lvl. 10
Champion's Greatsword: 147 Karma
Greatsword, Weapon Strength: 178 – 196, +14 Condition Damage, lvl. 9
Champion's Mace: 98 Karma
Mace, Weapon Strength: 160 – 180, +7 Precision, lvl. 9
Champion Plague: 105 Karma
Accessory, +4 Condition Damage
Pit Winner's Cloth Chestpiece: 126 Karma
Light Armor, Defense: 34, +7 Precision, Lvl. 7
Pit Winner's Leather Chestpiece: 126 Karma
Medium Armor, Defense: 37, +7 Condition Damage, Lvl. 7
Pit Winner's Chestpiece: 126 Karma
Heavy Armor, Defense: 39, +7 Condition Damage, Lvl. 7
Crude Salvage Kit: 28 Karma