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