Here is the full list of all 12 Fortix achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Capture 100 powerups.
Capture a powerup while you are under the effect of an other powerup.
Capture Xitrof.
Capture one of each enemies.
Capture a catapult trigger when there is no more turret left to shoot out.
Conquer at least 40% of the playfield with a single capture.
Capture at least 3 triggers with one capture.
Complete every level to perfect on any difficulty.
Finish the game on Impossible difficulty.
Capture 100 dragons.
Destroy all towers (at least 2) on a level with a single capture.
Let Xitrof lay 15 eggs on the final level, then win the level.