Defeat General Gaius

Gaius is the games final boss. There are four phases, with each phase adding something extra to the fight. There's a shop right before it where you can buy as many revival stones as you can. The game ends here anyway so it's good to make it as easy as possible.

Phase 1: He has a forward charging attack while on the ground, and an uppercut followed by a dive. He'll dodge or parry the majority of your melee strikes, so projectiles are the best damage dealers here. Jumping towards him and challenging him in the air seems to be the most effective strategy. When you jump, he'll also jump. Meet him in the air with some melee strikes and a throw if he doesn't parry. You can repeat this over and over and he'll almost never use his other attacks. Use projectiles whenever you have enough energy.

Phase 2: This part adds electrical orbs that spawn at your position, and you'll be bombed by flying machines. Same strategy applies here, but you'll want to avoid the orbs as they do a lot of damage. Use your projectiles to take down flying machines quickly. Try not to attack when he casts the orbs. If he parries, you can get knocked into them.

Phase 3: The same as before, except now you have to deal with the orbs in a confined area. There are 2 bombs that you can use to your advantage.

Phase 4: Watch out for the lava below. Try to stay on the main platform on top. My strategy here was spam projectiles and kill him fast as possible so I wouldn't have to deal with falling in the lava. Remember that food items restore your energy in addition to your HP.