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