Fantasy AGE is cool. I'll give it that. But Titansgrave doesn't convey fast, and after eight episodes, I still don't understand the stunt system.
Going purely from watching the show, it seems fairly straightforward. They have a quick-reference card of various stunts (which by now they seem to have memorised), each of which cost a certain number of points.
If they get doubles on their dice roll and score a hit, they gain a number of stunt points equal to the value of the 'stunt die' - the one die in their set that's of a different colour. They can spend those points invoking whatever combination of stunts on their attack they can afford.
Stunts they've used seem to include one which allows an extra die of damage, one which halves the target's armour value for that attack, and one which allows a follow-up attack.
For non-combat rolls the system seems much looser, with a sense of stunt points "making cool stuff happen", but that may be subjective.