The Dark ing is weak to the spell Cure, so just use Cure on him 2-5 times while using Phoebe as both your healer and to cast White
On any battlefield that rewards Experience points, keep fighting encounters until you have just one battle left.
Then go anywhere else and continue fighting enemies until the amount of experience you require to gain the next level is about the same as the experience awarded per fight back at the earlier battlefield.
Return and complete the battlefield, which should cause you to gain a level from the the experience awarded from enemies, then another level!
One way to achieve this arrangement is grab the Seeds in the Bone Dungeon first, then get the Cure Potion from defeating the Flamerus Rex. Then go to the Ice Pyramid and grab the Refresher, then try and get the Heal Potion next in the rightmost chest in the room where you also find the second chest armor. After defeating the Ice Golem, obtain the coin and head for the Hotel in Fireburg.
Use all of your Seeds until you have none left, then talk to the NPC behind the counter on the right. You can purchase more Seeds more him, so what you want to do is attempt to buy 0 (zero) seeds. Confirm your selection to have a new batch of "zero" seeds in your inventory. Use one of them, and the Cure Potion already in your inventory should glitch and turn into the Sun Coin; normally this item is needed to progress through Doom Castle. Now talk to another NPC sitting at a table to the left of coin seller. Buy 19 Cure Potions from him.
This triggers another glitch where the two coins you have already earned through story progression change into two new coins needed for the remaining dungeons. That means you are free to head to the Focus Tower and continue your journey earlier than expected, without needing Reuben.
Look for a battlefield with enemies that can use the selfdestruct ability. During battle defeat all other enemies except for the one that can self destruct. Next, ensure that your character's HP has dropped low enough that the selfdestruct will drop it down to 0. Wait for the enemy to use the ability, allowing it to defeat both itself and your character in the process.
You will still be rewarded with the experience and GP, as well as the option to try the battle again. Repeat this process until you earn the prize for clearing all encounters on the battlefield. Restart the battle again and defeat all enemies as normal this time. The battlefield round counter should read something like 255 of out 10, for example.
Curiously, you can use this game to check the version number of the chips used in your SNES. To do this, simply press Start + Select at the same time on the menu. The text may appear glitchy after performing this: simply exit and reenter any menu to fix this.
In Doom Castle, you fight a boss called Skullrus Rex. He is another version of Flamerus Rex from the start of the game.
Swipe him with the Dragon Claw and he falls, in one hit.