Ou, the Mountain God

Ou, the Mountain God is a boss found in Children of Morta. He is the final boss you must face.

Strategy
Ou's fight is broken up into four distinct phases. For the sake of this strategy guide, I will refer to the top, right, bottom, and left of the screen as North, East, South, and West, respectively.

In phase one, Ou has three attacks: One of the attacks is a conal blast of spherical projectiles that will always face "South". After this attack, he will always use the second of his three attacks, which is a point-blank AoE around his hitbox before teleporting to the center of the stage. In order to handle these two attacks, the player can bait Ou to the Southeast or Southwest corner of the arena, then Evade behind or to the East/West of him in order to avoid the attack. Ou is animation locked during the cast of the spherical projecticle attack, so here is the player's opportunity to deal some damage to him. the player can avoid his point-blank AoE by playing Linda or Lucy, or attempt to time it perfectly with a melee character. I recommend using Linda or Lucy, as their mobility will be helpful in later phases. Ou's third attack in the first phase begins with him teleporting to the center of the arena. He will conjure a staff that appears to be made of two keys, then cause telegraphed AoE markers to appear around or on the player character. These AoEs don't necessarily spawn on top of the player, so it's possible to move minimally during this attack to maximize DPS. When Ou's HP reaches somewhere between 70-50%, he will move into phase two.

In phase two, Ou will summon Dark Claw s, (possibly) Dark Waller s, Dark Wizard s, and Dark Jelly Dad s to attack the player while they're avoiding his other attacks. These enemies can be largely ignored by kiting around the arena in a clockwise or counter-clockwise pattern, given enough movement speed. It's important to note that, like other bosses, Ou will not summon additional adds unless a specific number of the initially summoned adds are killed. That being said, it may be beneficial to kill all but three adds to make completing this phase easier. During this phase, Ou will, generally, float around the center, Northeast corner, and Northwest corner of the arena. He will conjure gem-like projectiles just above/North of his current position that orbit around an invisible, intangible object. These projectiles slowly expand outward before breaking up into smaller projectiles, adding a minor "bullet hell" feel to the phase. Fortunately, the larger projectiles can be hit with ranged primary attacks into Ou in order to deal damage to him. This is not necessary to end the phase. Ou's third main attack during this phase is what I call the "Kaleidoscope Beam." Ou will stand still momentarily and create a telegraphed, conal AoE marker that covers from his position to the Southmost wall of the arena. He will sweep this beam back and forth, chasing the player. After a few seconds, the beam will lock into place before firing and dealing damage to the player if they're inside it. This attack can be baited if the player character stands in one place for long enough. The player will need to Evade at the right time, as the beam locks in place, to avoid damage. Something that I'm unsure of, because I do not remember, is that Ou may use his third attack from the first phase during this phase as well. When Ou reaches around 25%, the phase will end, play a cutscene, and the third phase will begin.

The third phase begins with the player character inside a bubble of light conjured by Anai-Dya. I do not know if leaving this bubble causes periodic damage to the player. Inside this bubble is John Bergson, or (possibly) Linda Bergson if the player is playing as John. The phase (possibly) requires the player to revive John by pressing F, by default, in order to progress. During this phase, a number of adds will spawn in the dark, corrupted areas of the arena. The adds that spawn are Dark Claws, Dark Wizards, Dark Shaman s, and (possibly) Dark Jelly enemies. The reviving process is interrupted when adds deal damage to the player, so distract (via totems or Lucy's Decoy) or defeat the adds before reviving the family member. After reviving them, Anai-Dya will begin walking West, Southwest, then North until they reach the Anai of Barahut (the desert one). Along the way, adds will spawn and attack the player. It's recommended that the player defeat them before arriving at the second Anai, as arriving there will trigger more adds to spawn. In the second Anai's bubble, the player must revive two fallen Bergson family members. After killing the adds and reviving them, the second Anai will search for the third Anai (the machine one). This process is identical to how Anai-Dya searched for the second Anai, albeit his walking pattern is different. After dealing with the spawned adds and reviving the last two fallen Bergson family members, the fourth phase will begin.

The fourth phase is, from my experience, the easiest of the four phases. During this phase, the player fights alongside the other five playable Bergson characters to defeat Ou. These five other characters are NPCs and, I assume, are the same level as when the player last played them. Ou will summon adds during this phase, but assuming the other playable characters are leveled somewhat, Ou will die within seconds and the battle will end. The game's final cutsene will play after this. Congrats! You did it!

(Guide written by Sky Rimeheart, @TSMSky on Twitter)