Phantom King is a sub-boss guarding the way forward on the 190th floor of Tartarus. It is neutral to Panic and blocks all other elements.
Phantom King has two means of attack: either instant kill via its Light spells or pure damage via Mind ChargedMegido. Bring Ken for this fight, since he is immune to Light and the ability to heal any damage dealt by Megido. As the Phantom King also tends to force party members to skip turns with Fear (but, fortunately, doesn't know Ghastly Wail which can kill them), either protect against it, bring a Persona that knows Me Patra, or stock up on Me Patra Gems to ward off the ailment. However, since this boss (unlike the two preceding it) is fought as an individual and since it carries no affinities (excluding Light/Dark), the party shouldn't have too much trouble with it. Virus Breath will frequently miss when used; however, the Phantom King is susceptible to the Panic ailment, leaving it open to critical hits from physical attacks.
Phantom King also takes adjusted damages from each affinity: Slash attacks will deal 125% damage, and everything else save Almighty will deal 75% damage.
Phantom King reappears later in the second and third section of Empyrean within the Abyss of Time as a regular enemy. It maintained the same elemental affinities as its sub-boss variant.
In Golden, Phantom King appears in Worlds 5 and 6 of Magatsu Mandala. It is also resistant to Physical and Wind attacks, but gains a weakness to Electricity. It may use Mahama to instantly kill party members, the chance of which may be increased with Stagnant Air. It can also attack with Agidyne, amplified by Fire Boost. It may also drop Rainbow Quartz for trade at Shiroku Pub.