Hearthpwn

Gelatinous cube and this thing? Holy shit. You gotta kill it otherwise it gets cubed but if you do kill it you are losing to nzoth

unless of course you are playing gainst razakus priest, then you are fucked

I didn't want to have to do this... but you've left me no choice. I'm done taking shots in the dark, it's time for action, I'm going to...

Make A Spreadsheet!

By carefully analysing each and every card hearthstone has ever released I will be able to pinpoint all three cards. Wish me luck, for I am going past the point of no return

Could it be Wilfred Fizzlebang?

the power to abuse is the 'all the cards you get off your hero power costing zero'

short fuse could refer to how he immediately gets killed

jaraxxus is blocking the sun so that covers the sunglasses line

in the last lines of the riddle it could be referring to the wow thing where the horde and alliance had to fight jaraxxus

I think it's fairly ok. It's basically a card that says have a board clear or lose. Although many decks will have a board clear others will not, or at least their board clears will be few and varied. As the name suggests it is the 'finishing' card. If you are playing a priest or warrior as midrange shaman it is pretty easy to exhaust their board clears early on and if you already have the board when you play the combo it will be really hard for a full clear to come out barring brawl and twisting nether (think 7/7 things from below and 4/5 feral spirits). It is quite possible this card might see play