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