Lunar Bahamut is an optional boss in the Game Boy Advance and Playstation Portable port of Final Fantasy IV. It is fought during Kain Highwind's Lunar Trial at the Lunar Ruins. When beaten, the player obtains the Dragoon Gloves, which increase Kain's stats and changes his Jump command to Double Jump, the Abel's Lance, and the Grimoire LB, which, if used as an item, summons Lunar Bahamut to deal 9,999 damage to all enemies. Using up the Grimoire unlocks the trial door again. Defeating Lunar Bahamut a second time nets the player a Megalixir.
This is a hard battle, as it must be fought with Kain alone. Before entering the trial door it is recommended to have some Lunar Curtains or Light Curtains and some Hermes Sandals (none are required, however they make the battle a lot easier). When the battle starts Dark Kain is fought, but a single Jump causes him to counterattack and transform to Lunar Bahamut.
Kain should use a Lunar or Light Curtain to avert the Megaflare attack which follows after a three second countdown. Using a Hermes Shoes can be an advantage to avoid the attack and be able to use Jump twice before getting damaged. Any damage should be healed with a Hi-Potion or an Elixir.
If the player has no Curtains or Sandals, one may have to reset the battle several times before one gets the "feel" of timing the Jumps properly (which is ultimately what the battle depends on). The best time to do so without using Sandals would be right after the count of two. Any earlier or later merits a Mega Flare.
When Curtains aren't available, another strategy is to buy 30 Elixirs, then when you battle him (still the same, use buff items like Hermes Shoes if needed) Jump after the countdown hits 2, then after attack he counters with two attacks (that cause 900+ - 1500+) use an Elixir, then he uses Mega Flare again, then again use Elixir then Jump, then do the same again and again.