

That and more really. You could use it to do a green screen effect, but you can also use it to adjust color balance, brightness or do weirder things like swapping values between colors. It gets really crazy when you are working with full video because the time of the current frame is also available to be incorporated, so you can even do animated effects.
Another powerful filter is the convolve filter. That allows you to apply matrix transformations, which can for example be used to apply a homography matrix and adjust a videos perspective.










This is pretty close to how aging used to be portrayed in D&D so should be good there.
This sounds like it will be absolutely brutal. You say d20 dc10, does that mean you intend to roll unmodified? A 50% chance to give yourself disadvantage on all ability checks on the first successful attack feels like it would snowball quickly. Maybe dial it down somewhat to something that will trigger, but not as often. Also having to roll another check and d4 damage sounds like it would add a lot of time to his turns. Maybe instead you could give him disadvantage on saves against exhaustion causing effects? You could do a similar mirror to your ability score modifications and give him advantage to resist some effects thanks to his experience. Maybe charms or illusions.
I like where your head is at with the battle master. When I did a retired character back in the day the campaign side stepped the age modifiers, since they were no longer relevant, but I used the crusader class from Tome of Battle with a similar theme in powers. Went with a lockdown spear wielder for other character choices. Good luck with the campaign, sounds like it will be a fun time.