Accomplish the indicated achievement to get the corresponding number of Gamerscore points:

Dragon Knight (99 points): Finish the game.
Chicken Out (25 points): Kill Casper.
She Never Saw It Coming (25 points): Scare away the fortune teller.
Bounty Hunter (100 points): Bring to justice all of Rivellon's most wanted criminals.
Turn a Blind Eye (10 points): Cure blindness.
Pillar of Strength (100 points): Upgrade all your Battle Tower platforms to their maximal potential.
On the Run (5 points): Send one of your runners on a mission.
Peeping Tom (5 points): Read someone's mind.
Off the Leash (5 points): Summon your creature.
Gaining Power (5 points): Level up once.
Divinity (40 points): Reach an epic level.
Prince Charming (5 points): Charm an item.
Enchanté (5 points): Enchant an item.
Master Brewer (5 points): Create a Potion.
Mater Studiorum (5 points): Make use of your skills trainer.
Shop Till You Drop (5 points): Trade with someone.
Shape of the Dragon (5 points): Morph into a Dragon.
Mirror, Mirror (5 points): Make use of an illusionist's services.
A Dragon Stone's Throw Away (5 points): Use the Dragon Stone.

Additionally, there are 22 secret achievements:

All Aboard! (25 points): You finished Farglow. Happy hunting!
The Dragon Roars (25 points): You have destroyed Damian's armada and successfully protected your Battle Tower.
The Maxos Baedeker (20 points): You have found the book that will lead you to the Hall of Echoes.
Spell-Struck (25 points): You have found the spell that will reveal the Hall of Echoes.
The Damned One (10 points): You met Damian.
Lovis Lore-Master (25 points): You correctly answered all of the questions about Lord Lovis.
Path of the Pious (25 points): You have gained entry to the Maxos Temple.
The Feral Fjords (10 points): You have discovered the Orobas Fjords.
Hold the Key (15 points): You have obtained the key to the Maxos Temple.
The Great Escape (20 points): You have made it out of the Maxos Temple.
Cave In (25 points): You have found Adah and Mahalath's secret cave.
Dragon Ho! (25 points): You have found a true Dragon: the Patriarch.
Dim Lights, Dark City (25 points): You have discovered Aleroth.
Shielded (25 points): You have obtained the shield that will protect you in the Hall of Echoes.
Bunny Bagger (30 points): You have killed the Killer Bunny.
Castle Crasher (80 points): You have destroyed all of Damian's Flying Fortresses.
The Sigil, the Seal (25 points): You have found the seal that will open the gate to the Hall of Echoes.
Adrift (30 points): You have found Michael's raft.
You're Going to Die, Charlie (1 points): You have killed Charlie the goblin.
Family Fortune (30 points): You have read the mind of the three Gremory siblings.
Saint or Satan (20 points): You have shown you are either utterly good or evil in Bellegar's cave.
Past the Gates (25 points): You have reached the Hall of Echoes.