My legacy was idling rough almost like it wanted to stall. If I give it gas, it hesitates. Then this morning, it didn't want to start at all. The abs and traction control lights came on and the odometer reads ER SS

I had someone put it on a code reader and the only thing is said was there there was a misfire.

That's right! The code was PO301-4, the last digit incicating which cable was shorting to ground because of wetness or too-close proximity to exposed metal. So twist the coil/cable boots so that the cables aim a bit away from the intake manifold metal, and check along their lengths for sitting against metal on their way to the plug boots. (Also ensure that all boots are FULLY pushed onto the plugs.) Retest. If only one 30x code, maybe pull that plug and check for oil-fouling or a blown-off plat anode, as the OE NGK plats are famous for popping off their heads! If you keep getting misfires you might have a cracked coilpack tower or internal short to base. Pretty common. I have a used one on eBay for cheap if you need it. MANY misfire codes will self-correct following 2-3 clean restarts IF moisture has dissipated. Although changing plugs on the 2010+ is a PITA I'm heartened to see that Subie went to individual coilpacks with low voltage cables. Hopefully these won't become intermittent with old age, like the VW's.