Deriving Damage from Guidelines?

I have 2 questions really

1.) Where do you get +10 damage from with the crystal dart? In the MuTe guidelines there is no mention of any damage.

2.) Spell for picking apart :[i] The waters of Perdition /i (base 4, +3 sight,+1 Conc)
R : Sight D : Conc T : Individual

Changes a stream of water (the natural feature) into raging flames along it's length. Question : If you wanted to save the fish, would you add a ReIg(An) effect?

And related to question 1, where would I obtain the damage from the flames?

Thanks All

Usually you take the Creo Ignem guidelines to look up damage.

It is tacitly assumed that all other combinations are one magnitude higher Tan creo ignem.

That means Base 15 gives you +15 damage (unless it's Creo ignem, which gives you +20).

1.) The Crystal Dart is a legacy spell from Ars 4 so the damage value follows no guideline.

1st edition as it happens. Though the damage has changed a bit, it used to be +8.

Rego requite would be enough to control whom you do not want to burn with the flame. As it happens in this case you also need to think about how these fish are going to breath in fire...