On Dissidia Duodecim, you need to Finish Scenario 012, then either finish scenario 013 or buy scenario 000 from the PP Catalog which costs about 2000, after that you have to go through multiple gateways on the new scenario until you eventually get to feral chaos, first encounter is level 95 and second is level 130. if you mean the way to fight him, basically the same way as other characters, dodge/block his attacks and hit him with your attacks.
firion. just use rope knife and double trouble and that's it.
^i haven't tried that yet, maybe i should do that now..
- The way I did it was I used Golbez and spammed Genesis Rock repeatedly until Chaos died. This, however, took incredibly long and was tedious. But thanks to the fact that Genesis Rock can be used to drag enemies from the bottom of the level to the top, you just need to stay above Chaos and you'll hit him every time without having to get too close. Also, the attack ends with a wall rush due to the small level, so you have time to begin the attack again while Chaos is recovering from the wall rush. 188.8.131.52
^Also golbez ground HP attack "nightglow" also works extremely well when he is above or near you. Because golbez becomes almost invinsible when performing nightglow you have time to plan your next move or when he is close to you suck him in. Also again with wall rush you can buy time. Combining it with Genesis rock makes golbez a very handy party member during this fight.
A very easy way of beating feral chaos is getting Bartz's flare as in holy to flare and spamming it above him until he dies. Whatever you do, don't fight him melee on the ground.