Here is the full list of all 30 Gleamlight achievements.
Defeated the annihilator, and gained a new power.
Saw it all with the child
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.
Summoned a child in a destroyed world.
Died 100 times.
Defeated the dark being within a new journey.
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 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.
Defeated 100 machines.
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 the free-flying, and gained a new power.
Defeated 10 machines.
Defeated 100 ghosts.
Defeated the devoted, and gained a new power.
Defeated 50 ghosts.
Defeated 10 ghosts.