In the RPG, a death curse is treated the same as a thaumaturgic ritual. Now, with a normal thaumaturgic ritual, you take your time, gather a bunch of elements for it, and cast over a long period of time mostly for the sake of your own safety, because if you blow a roll, either you eat
all the power to make it work (and you probably die), or your 30-shift ritual goes down the drain and blows up everything around you.
(Sidenote: This is another reason more wizards is better for casting -- you can divide up the backlash if someone screws up. 30 shifts of damage will obliterate most lone wizards, but divided among 13, it's barely a headache.)
With a death curse, you're already dying, so none of the "careful" stuff is necessary -- you can cast the whole thing, instantly, and just pour all your resources into pure power. You essentially use yourself as a sacrifice, so you get power for every potential consequence you haven't used yet (20 shifts on a base human alone), plus some more based on your stats (for someone like Harry, that's another
, plus you can tag every consequence you have used, and can throw all your fate points into it because, hey, it's not like you're gonna need them afterward.
The result is something like a 30-ish shift effect for the average wizard; for reference, the heart-exploding spell from Storm Front was 35 shifts, while a "strong" fireblast like Harry's is 6. So 30 shifts is a
lot to work with, especially if you're not directly attacking.