Here is the full list of all 30 Gleamlight achievements.
Defeated the devoted, and gained a new power.
Defeated the free-flying, and gained a new power.
Obtained the dark being's sword, and gained a new power.
Defeated the free-flying once again, and gained a new power.
Defeated the road block, and gained a new power.
Defeated the approaching giant, and gained a new power.
Defeated the destroyer, and gained a new power.
Defeated the ruler of the skies, and gained a new power.
Defeated the annihilator, and gained a new power.
Died 100 times.
Defeated 10 ghosts.
Defeated 50 ghosts.
Defeated 100 ghosts.
Defeated 10 machines.
Defeated 100 machines.
Defeated a dark being resembling yourself.
Defeated the demolisher of the human world.
Defeated the devoted within a new journey.
Defeated the road block within a new journey.
Defeated the free-flying within a new journey.
Defeated the dark being within a new journey.
The dark being opened a road further in.
Defeated the singularity of all.
Save data erased.
Defeated the dark being, and watched the credits.
Defeated the demolisher of the human world, and watched the credits.
Summoned a child in a destroyed world.
Journeyed to the end, and watched the credits.
Summoned a child in a revived world.
Saw it all with the child