The castle is crawling with enemies. First you'll fight two groups of knights. If you keep to the left you will fight fewer at a time. Eventually two Green Thieves will arrive. Hit them for a Heart. After this you'll fight a couple of those hammer-wielding giants. This is a tough fight as they have a lot of health and are in a tighter area.
After them you will fight some more basic enemies followed by two minotaurs. The trick with the minotaurs is that there is a chasm just offscreen on the right. If you repeatedly ram or jump-attack them you may be able to knock them far enough that they fall into the pit. Save your magic if you can.
After this you will fight three red knights (two if you pull back and only use the left-hand part of the screen to fight them) followed by some spearmen and clubmen.
After that at long last you can fight the Prince of Darkness. The Prince can swing his axe in a huge arc, can do jump attacks, can grab you and throw you, can block, and can hit the ground so three bits of flame come out. Every time he releases flames, do a jump attack or death jab.
He is flanked by two purple knights. Every time you kill one another will take his place until you've killed four in total (or six on hard). They will automatically die when the Prince does, so you might as well focus on him.
One way to defeat him is to move on a higher or lower vertical plane and then pull in at the last moment. You can also choose to wait for him to come to you and then charge him, but if you time it wrong he'll block or throw you. Just like the minotaurs he'll use his wide swing any time you come near unless he is performing some other action at the time and can't change to a wide swing in time.
After defeating him you may or may not fight him a second time. It seems to depend on whether you used the level select cheat.
Good Ending[edit]
If you get to fight him a second time he is alone but his attacks do much more damage. He also has his own magic, which he will usually use when you get too far away from him.
When he's finally defeated once and for all the castle, held together by his magic, starts to crumble. Your character grabs the golden axe and flees as the ceiling caves in.
Your character(s) then travels backwards through the levels you chose. At the end you will reach Gilius, and there you will see the heroes you freed during your journey (if any). You are told peace has returned to the entire land, and that your adventures become legends that pass down through the ages.
Bad Ending[edit]
If you didn't get to fight him again you're informed that you were unable to retrieve the golden axe and that you must journey again to bring true peace.