You place an enchantment on yourself. If the enemy is casting a fire spell, the ward triggers and sends a wave of cold towards the spell, completely dispelling it if it is 2nd tier or lower and potentially also hitting an enemy. If the wave of cold hits an enemy it will be paralysed for 1 turn and take 12 damage. An agility throw of 1 is needed to avoid the wave of cold if it attempts to hit the target. The spell can stack multiple times, blocking multiple spells and potentially dealing more damage.
At Higher Levels. The enchantment automatically applies 2 stacks on you, and the maximum amount of enchantments stacked is doubled. In addition it now also dispels 4th tier fire spells and lower. The paralysis lasts a turn longer and deals 8 more damage.
* - which you take when you see a creature within 20 feet of you casting a spell
There is no such thing as a “agility throw” also you need specify how many dice you can’t just say “12 damage”