The screen now reads FINAL SCENE in big letters so anyone watching can be duly impressed with your gameplaying prowess to get this far. And certainly by this point many may be down to their last quarter.
Final Death Adder Strategies
Use all the techniques as before. It's such as small arena that you will have trouble not getting hit by his Ring of Cloudy Evil power, but he has less chance of avoiding a death-jab. Use your magic (if you have any left) or just keep hitting him until he's finished. This is an especially good location for the cooperative attack. Instead of dying, DA jumps into the middle of the platform and says (through text) "Chew on this guys!" He now summons a halo of energy above his head. Don't even try to attack him; he'll repel you and you'll get hurt. Just wait.
Cutscene: now suddenly all four heroes are on the platform together (even the ones you and your buddies didn't use). But wait! Goah's backpack is empty! Where is Gilius? Suddenly he bursts down from an unseen location and strikes DA smack in the center of his skull. They both fall off the platform and there is an agonising combined scream from them. They explode into a cloud of magic dust. The others stand on the dragon's back with the axe behind them, and silently fly onwards as the classic "Fin" displays onscreen.
Ending Scene
Now you see a big room. All the villagers and freed prisoners you saw fleeing appear one by one in the room. Then the players arrive. There is the feeling of a party in the air. The various bizarrians and enemies appear, and finally DA himself. Then the players are rewarded with a big banner like on the title screen, saying "See you next game!"
It seems this is saying DA and Gilius didn't really die as they live on time and time again every time you play the game again. The game doesn't scroll any credits, so you are left to assume that some of the authors of the original were involved.