Here is the full list of all 50 Eldest Souls achievements.
Reach the ending without dying once.
Hit enemies with a Shard attack 200 times
Have at least 10 Windleaves active at once.
Perform 3 Perfect Counters in a row against any Boss.
Gain the Abyssal Eye
Gain the Kindled Heart of Fire
Finish the game without activating any Shard or Infusions.
Gain the Blessed Hunter's Charm
Defeat Eksyll in Abyss Mode.
Defeat Drakmur in Abyss Mode.
Defeat Drakmur, the Nightmare while taking 0 damage
Defeat Aryana in Abyss Mode.
Defeat Aryana, First of the Moon while taking 0 damage.
Defeat The Warden of Purity in Abyss Mode.
Defeat The Deer God and the Warden of Purity while taking 0 damage.
Defeat The Deer God in Abyss Mode.
Defeat Hyem in Abyss Mode.
Defeat Hyem while taking 0 damage.
Defeat Azikel in Abyss Mode.
Defeat Azikel, God of Light while taking 0 damage.
Defeat Eos in Abyss Mode.
Defeat the Watchdog while taking 0 damage.
Defeat Eos, God of Unity while taking 0 damage.
Defeat the Guardian in Abyss Mode.
Defeat the Guardian while taking 0 damage.
Defeat Eksyll
Maintain 4 stacks of Berserker for 30s.
Reach the Steps of Ascension
Gain the Blessed Trueice Prism
Obtain the Empty Vessel
Defeat Drakmur, the Nightmare
Defeat Hyem of the Frigid Waste.
Deliver the bag of crowns to Edelon.
Gain the Blessed Feather of Dawn
Defeat The Deer God and the Warden of Purity.
Defeat Aryana, First of the Moon.
Reach Concord Sanctuary
Defeat Azikel, God of Light.
Defeat Eos, God of Unity
Hit enemies with a thrust attack 200 times
Hit an enemy with Windslide, Berserker Slash, or Counter 20 times.
Retry a Boss 10 times in a row.
Reach the Crossroads
Defeat the Guardian.
Die to a Boss.
Talk with Rass
Deliver the harp string to Edd
Defeat the Watchdog.
Die to a rolling log.
Reach Crusader's Landing