Lyric discussion by SomethingBatman 

Cover art for Mercenary lyrics by Panic! at the Disco

The spoken part is the Joker speaking because this is a song for/about Batman and it is in the Batman: Arkham City video game soundtrack. And I'm not sure if it is a xylophone (because I am so used to marimbas) but it defiantly sounds like Mona Lisa and I thought that from the very first time I heard it.

Here are some things that I picked up on from the lyrics.

"I dodge the blast and apologize for collateral damage" is about how Batman does just that. He takes all the heat for what the villains do when he's the one trying not to be killed by them.

"I want to make you quiver, make your backbone shiver" is about how Batman wants the villains to fear him because he is the vengeance and the night.

"Hey kid, take the stage and deliver" is about Robin.

He is a mercenary because he thinks that he is only acting for the reward of revenge.

it's definitely Hugo Strange speaking, not the Joker. it's not Mark Hamill's voice, it's Corey Burton's. also he's asking Batman how it feels to stand where his parents died because Hugo Strange finds out he's Bruce Wayne in the game.

@SomethingBatman The song wasn't made specifically about batman, the song's about a wanderer kind of like Batman as a vigilante. Brendon Urie even said himself the actual song doesn't relate to Batman directly, he said it was about a wanderer.