Eight Overlords, three acts and a true ending you lose by finishing off the King
How each Overlord is fought, what each one unlocks — the modifiers after Bastion, the Grapple, the Parry — and the game's only decision: in the second King fight you have to go through the gate without finishing him.
And it counts towards Bastion, Rhabdom, Legion, Architect, Shepherd, Priestess, King, Let Go, Never Let Go, Into Yellow, The Blazing Throne, required for the platinum.
From Prophet to King: what each does and what it opens
All eight Overlords are hidden and range from 64.0% to 34.4%: half of those who kill the first kill the last.
Prophet (Shattered Rise, 64.0%): three bars and only takes damage on its weak spot, which opens once the yellow buds on the sides are destroyed. Absorb the blue barrages to charge the Power Weapon and dodge the three corrupted waves.
Bastion (Ancient Depths, 54.8%): no weak spot, shoot from the start. Between bars there are stationary bots to kill, and from the second bar it fires red Nova that cannot be dodged through: use the jump pads. Killing it unlocks the Carcosan Modifiers and the Banyan Tree.
Rhabdom (Shattered Descent, 51.2%): a single bar, the easiest in the game. That biome also gives the Grapple and OverDrive.
Legion (Blighted Marsh, 46.7%): a flying horde, but only the central red enemy hurts the boss. This biome gives the Parry: send the red Nova back.
Architect (Desecrated Fortress, 42.6%): flying and constantly moving; Handcannons or Rifles, which auto-aim, and no Shotguns. It destroys the platform with each bar; if it knocks you off, grapple back. Closes Act 1.
Shepherd (Acolyte's Haven, 39.4%): the boat's tentacles first, then the head. Absorb blue and yellow, parry red.
Priestess (Cathedral, 37.3%): kill two of the three small priestesses for her to appear; on the second bar destroy the three red chimes instead of fighting them; on the third, collapsing platforms. Closes Act 2.
King (Yellow Shore, 34.4%): one of the easier ones, since he fires so many absorbable projectiles the Power Weapon never stops. First bar blue only; second red Nova only; third, yellow. Closes Act 3 and rolls the credits.
The Epilogue and the gate you have to go through
The three acts are automatic trophies: Never Let Go (42.6%) with Architect, Into Yellow (37.3%) with Priestess and The Blazing Throne (34.3%) with the King and the credits. Their percentages are identical to their bosses': nobody stops in between.
But the credits do not close the game. Back in The Passage the objective "Face Tomorrow" appears, sending you to specific rooms in several biomes — one is the fourth Banyan Tree entry, the one that completes Shattered Glass. Once done, it is back to the Yellow Shore to drop the King again.
And here is the game's only decision: when his third bar runs out and he collapses, do not walk up to finish him. Go through the gate while he is on the ground. That gives the true ending and Let Go (22.4%), one of the two golds.
The drop from 34.3% at the credits to 22.4% at the true ending is a third of those who finish the story: some do not know there is an epilogue, and some finish the King out of habit.
In the second King fight, when he collapses, do not finish him: go through the gate while he is down. That is what gives the true ending and Let Go.
The trophies involved
Each one links to its section inside the full Saros trophy guide.