This guide's sole purpose is damage, and burst, EPIC burst. Some things you need to know before reading this: Q = Baleful Strike, W = Dark Matter, E = Event Horizon, R = Primordial Burst.

For the sake of this demo of his damage I'm going to make two assumptions. The first will be an assuming you only farm 17 ap with baleful, and the second assumption will be farming 217 ap with baleful (the ap I farm fairly often game). The general burst goes a little like this. E -> W -> deathfire -> R -> Q, making sure the E stuns before doing anything else. Now lets see how much damage that will do.


SITUATION 1 (17 farmed ap terrible):
so you have 500 ap at level 18.
E - no damage
W - 320 (+500) = 820 damage
Death Fire - 30% (+17.5%) = 47.5 % current hp
R - 500 (+600) = 1100 (pretending the target has 0 ap)
Q - 260 (+ 300) = 560
auto attack with lich bane - 500 damage approx

that's a grand total of 2980 damage (enough to one burst any non tanky champion EASILY) + 48% of their health (if you use death fire properly), meaning if the death fire is used properly you can even one burst a tank.

SITUATION 2 (farmed 217 ap):
so you have a total of 700 ap
E - no damage
W - 320 (+700) = 1020 damage
Death Fire - 30% (+24.5%) = 54.5% of current hp
R - 500 (+840) = 1340 damage
Q - 260 (+420) = 680 damage
auto attack with lich bane - 700 damage approx

This means a grand total of 3740 damage (enough to drop any tank w/o magic resist) PLUS 54.5% health (if used properly) this means if u target the right people (and you have just a little bit of luck) you can burst two people dead instantly simultaneously.

FOR EXAMPLE I will use this random cho build: (http://www.mobafire.com/league-of-legends/build/solid-chogath-solo-top-tank-158024)
and this top rated leblanc build (http://www.mobafire.com/league-of-legends/build/leblanc-insane-mid-62761) I am also assuming you have 700 ap.

So if you get a stun down on both of them and they are in the same spot, you throw down your W as per normal, then you death fire Cho (your deathfire will most likely hit before the W does) as he has the most hp (assuming 3700, meaning full 6 stacks) you then R leblanc and Q cho, followed by an auto attack on cho.
You just managed to deal 1850 (death fire on a fully stacked cho) + 1020 (your w) + 680 (your q) + 700 (auto attack w/ lich bane) for a total of 4250 damage on cho
and 1020 (your w) + 1340 (your R and it does even more damage considering she has ap as well) for a total of at least 2340. This means you just managed to take out a tank and an incredibly powerful mage by yourself in the span of about 1.5 seconds. CONGRATULATIONS

As you can see this build allows you to deal damage AND LOTS OF IT. It is a damage build and ONLY a damage build. You remain very squishy so be careful and avoid being focused.
I'll add pictures of my games and those little images of skills and stuff as soon as someone tells me how. I will also add more to this guide over time.

Try it and have fun :)
(I'll post a video of me getting a double in the span of 1.5 seconds later (I've done it 3 times but lol recorder wasn't on, it is very difficult and takes TONS of practice)