Here is the full list of all 45 Underworld Ascendant achievements.
Defeated a Ripper.
Killed an enemy without being detected.
Caused an enemy to be killed by Fire.
Enemies convinced to turn on each other.
Leap Boldly Ascendant.
Resolved a combat encounter against multiple opponents who detected me without taking damage.
Snuck by initial foes without being detected.
Caused an enemy to be killed by physics damage.
Switched a lever without touching it
Defeated an enemy without being damaged.
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.
Jammed a trap with an object.
Killed an enemy using a Deep Slug trail.
Gathered a key item without being detected.
Killed several enemies without being detected.
The world is your playground.
Caused a creature to investigate a sound, but was undetected.
Killed an enemy with a tripwire.
Successfully casted a spell with two runestones.
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.
Used Wall Run off a free object.
Killed an enemy with spells.
The Saurians passed this technique down for generations.
Pounced on an enemy.
Because the darkness should fear you.
A good fighter knows when to Parry.
Performed a combo attack with a sword, axe, or without a weapon.
Hid in a Deep Slug smoke trail.