Solasta: Crown of the Magister
132 Achievements
GOG
Fire at will
Kill 20 enemies using Fire Damage in a single campaign
38.4%
How to unlock the Fire at will achievement in Solasta: Crown of the Magister - Definitive Guide
There are tons of fire options in the game but the best for this by far is Fireball. Available on many classes, large AoE, powerful damage, and arguably the most effective spell you will get for the entire game. This should come naturally but just lob some fireballs if fire isn't part of your regular gameplay. Battle clerics and wizards are likely the two most common classes to have this spell, along with other random subclasses like the Oath of the Motherland paladin.