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