What makes this flashlight so powerful? A few things. First, there's some batteries. And not just a few, but 12 1.2V NiMH (rechargable) batteries capable of sustained 10 amp draws. They're in a nice, heavy duty battery carrier that can withstand the load as well.
Then there's the bulb. It's an Osram HLX 64623. This is a 12V bulb which is being overdriven to 14+V, to about 140 watts, with an estimated light output of about 4000 lumens. Compare that to a regular 2D MagLight, which is much, much less than 50 lumens.
There's also a metal reflector, as the stock MagLight reflector would melt almost instantly from the heat of the Osram.
The stock MagLight switch would also melt under the current load, so that's also been replaced with a switch capable of switching the load.