Dr . Lugae ( Final Fantasy IV boss ) Dr . Lugae , also known as Lugeie , Dr . Lugae , or Lugaborg , is a storyline boss in " Final Fantasy IV " . It is the fiend form of Doctor Lugae . After the battle , Dr . Lugae ' s Key will be obtained for use in the Tower of Babil to stop the cannons from destroying the dwarves . Battle . Lugae counters attacks with Sleeping Gas . He uses Poison Gas to poison the entire party , as well as Flamethrower and Beam attacks which do moderate damage . He also uses Laser , which can do upwards of a thousand damage and can easily kill a party member . Lugae may also cast Restore on the party , removing Poison . The battle changes in the 3D versions . Dr . Lugae will use Reverse Gas inflicting the Reverse status that can only be removed at the end of the fight , or if Dr . Lugae uses Reverse Gas again . The Reverse status causes damage and healing to have the opposite effect on the party and Dr . Lugae . He uses it as his first action of the battle and will continue to use it along with his other attacks . While the party members are under the Reverse status , Dr . Lugae will use restore on them to damage them doing around 600 - 800 damage . When they are not under Reverse he will use Flamethrower to do similar damage , although a character with Ice Shield or Ice Mail won ' t take as much damage . Dr . Lugae counters any magic cast on him with a Sleeping Gas attack . Strategy . In the 2D version , Rosa should heal after Sleeping Gas . Overall , besides Laser he is a simple and weak enemy to defeat . There are two ways to tackle the Dr . Lugae in the 3D versions . The easy way is to use two Elixirs on him when he uses Reversal Gas on his first move . Although wasteful , it ' s very effective . The other is to keep an eye on the Reverse status and not attack with any characters while having Rydia heal the party with Black Magic and have Yang charge up Focus up to three times while equipping the Lightning Claws until Reverse is removed . To recover HP while under the Reverse status , the player can make use of the attackers in the party to attack each other and gain HP . After Dr . Lugae removes the Reverse status with Reverse Gas , Rosa should heal while the others attack . Another way is to summon Whyt when Rydia is in Reverse status , which will remove it . If Rydia is brought back when the others are in Reverse , she will not be . This means that Rydia ' s status is a reverse of the other party members ' . Ergo , Lugae will use Restore when Rydia isn ' t in Reverse status , healing her , and will use Flamethrower when Rydia is in Reverse status , also healing . Rydia is effectively unable to take damage from Lugae ' s attacks . AI script . 2D . Whenever Lugae takes damage ( besides damage caused by summons ) - Sleeping Gas to random party member - Causes Sleep ( May Miss ) On First Turn Only = Poison Gas - Deals Light damage and Poison status to whole party . Turn 1 = Beam - Deals damage to a single party member , equal to 10 % of their total HP . Turn 2 = Laser ( ability ) - Deals damage based on Lugae ' s HP ; Lower HP = Less Damage Turn 3 = Flamethrower - Casts Fire on whole party Turn 4 = Heal - Cures whole party of status effects