Mulung is a early hardmode hell-dwelling boss made to be fought just before the first mechanical boss.
Mulung doesn't spawn naturally and requires the player to summon it with the Throbbing Eye while in hell at any time Mulung isn't already present.
During Mulung's first phase, three 'Servant of Mulung' enemies will orbit Mulung, the boss will be undamageable until these Servants are killed.
During this phase, Mulung flies around the environment targeting the player, occasionally dashing towards them.
Every 3-5 seconds it will shoot a 'chomper' projectile dealing 'insert dam' damage.
After all three Servants have been slain Mulung will be damageable, Mulung will no longer dash but will now shoot a spread shot of Chompers during this section of the phase.
After Mulung drops to one third health it enters phase 2. Three more 'Servant of Mulung' enemies are summoned, this time with the ability to shoot lasers at the player.
The Boss behaves Identical to the beginning of phase one, after the three servants are killed it enters its final phase.
In it's final phase, Mulung flies around shooting three lasers instead of Chompers,
~every 10 seconds, Mulung will also summon a Red Devil until it is defeated.
In expert mode, Mulung behaves the exact same till it's final phase. In Mulungs final phase it shoots a five spread pf slightly stronger Lasers although less frequently.
Every 5-10 seconds Mulung will freeze and randomly shoot lasers in all directions at the same time summoning a red devil. These lasers are much harder to dodge but do less damage.
Mulung was the first NPC and first ever feature added to Insidious
He was based off an old Boss from an earlier unpublished mod by the same developer, ModTest.