Here is the full list of all 45 Underworld Ascendant achievements.
Used Wall Run off a free object.
The world is your playground.
Gathered a key item without being detected.
Killed an enemy without being detected.
Resolved a combat encounter against multiple opponents who detected me without taking damage.
A good fighter knows when to Parry.
Enemies convinced to turn on each other.
Caused an enemy to be killed by Fire.
Jammed a trap with an object.
Caused an enemy to be killed by physics damage.
Successfully casted a spell with two runestones.
Defeated an enemy without being damaged.
Snuck by initial foes without being detected.
Switched a lever without touching it
Blocked an arrow with a held object.
A Mind Crippler was killed indirectly.
Jumped on a levitated box
Balanced on a plank.
Reflected projectile.
Caused an enemy to investigate a sound.
Killed an enemy with a trap.
Killed an enemy with a burning crate.
Killed an enemy using a Deep Slug trail.
Defeated a Ripper.
Killed several enemies without being detected.
Caused a creature to investigate a sound, but was undetected.
Killed an enemy with a tripwire.
Successfully casted a spell with four runestones.
Caused multiple enemies to be killed by Fire.
Dispatched an enemy who was bound while time was slowed.
Bound or stuck in place a creature, who was then dispatched by a trap device.
Killed multiple enemies with traps.
Caused multiple enemies to be killed by physics damage.
Rebranded a wand with a new spell.
Feed a Deep Slug one of it's favorite foods.
Resolved multiple quest objectives undetected.
Regained a massive amount of health using Arcane Regeneration.
Used "Merciful Fate" to cheat death.
Killed an enemy with spells.
The Saurians passed this technique down for generations.
Pounced on an enemy.
Because the darkness should fear you.
Performed a combo attack with a sword, axe, or without a weapon.
Leap Boldly Ascendant.
Hid in a Deep Slug smoke trail.