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