The man enters the room, clad in some sort of steampunk-esque suit of armour, complete with a respirator. He puts down his weapon, a military-grade flamethrower, on a nearby desk, then looks at you, the assembled recruits. He chuckles.
"Heh, quite a lot of you rookies over here. Propaganda that good? You'll change your minds, I think. Anyway, let's get down to business. They call me Tau. And I've seen stuff you can't even imagine."

The images flash before his eyes. They haunt his nightmares and infest every waking moment. A horde of mutated abominations approaches the battlements. The regular men there are torn to shreds within moments. Minimal resistance.

"Now, I don't know what you've been told to expect. But let me give you the rundown. If you're here for fame and glory," there seems to be a spark beyond his goggles, "leave now. No one remembers us. We're just the shields, that keep the horde away. Grunts without a face."

Some indeed leave. The horde overpowers the last signs of resistance and moves further toward the town, teeth gnashing and roars echoing.

"If you're here to get rich, don't fool yourself. You probably won't live long enough to enjoy the dough. Command also makes you buy your darned ammo."

Another few recruits leave. The final defence line readies its weapons, their trigger fingers itching.

"I see a lot of you here. So you want to protect queen and country? Noble. Or maybe... maybe you're here for the bloodshed? If so, you've found the best hellhole on this blasted planet."

The horde is no more. Some lay on the ground, burned to crisps, others are all over the place, after meeting a rocket head-on. Some received one precise round, others have more lead than blood in their veins Some were sliced to the tiniest pieces. The medic sprays his wound with government-approved magic, while assuring him he need not worry about any sort of homosexual attraction.

"Well, there's a lot of you. But only one is going to get dragged down to the depths of Hell with me. So, good luck on your final exam. Here's a tip," he almost lovingly strokes the flamethrower, "don't get burned. And hope you're as good as you think you are. I'll be waiting."