Here is the full list of all 34 Omensight achievements. It takes around 10-12 hours to unlock all of the achievements on Windows.
Unlock all other trophies
Defeat Draga in battle
Imprison Voden
Unlock the Kladen Seal
Defeat Ludomir in battle
Execute two Lethal Flurries in a row
Break a barrel thrown by a Shark while it's in the air, by throwing a barrel at it
Unlock the last Omensight
Use Lethal Flurry 20 times
Unlock Vera's Seal
Unlock all Harbinger's Blade upgrades
Kill 100 Rodentian fighters
Jump on the head of all your companions
Unlock all Harbinger's Aegis upgrades
Unlock your second Omensight
Unlock the Rodentian Seal
Defeat Indrik in battle
Use Phantom Grasp 50 times
Kill 100 Ciphers
Use Companion ability 50 times
Use Phantom Dash 30 times
Launch 4 Phantom Blasts while inside Delay of Fate's sphere
Kill 100 Pygarian soldiers
Throw a bomb towards a column while inside Delay of Fate's sphere
Launch a Phantom Blast on an enemy thrown with Phantom Grasp, while inside Delay of Fates' sphere
Use Delay of Fate 20 times
Unlock your first Omensight
Use Phantom Blast 20 times
Unlock all bonuses at the end of a day
Defeat Ratika in battle
Unlock the Pygarian Seal
Kill a surrendering enemy
Kill four enemies with the same column
Witness Voden's appearance for the first time.