Dependence between spells and spellpower

It seems you're asking about what attributes abilities scale with and how. Abilities don't just scale with attributes, they can scale with level as well! But not all do.

There are many modifiers, and all modifiers are multiplicative. Let's look at lightning bolt as an example

lightning bolt deals 847/975/1121(+stats, +level), So for level 1 lighting bolt, our damage is:

847*(stats modifier)*(level modifier)

=847*(hero_modifier*target_modifier)*(.101+.031*(HeroLevel-1))

=847*((100+HeroPower)/(100+Defense))^2.5*(.101+.031*(HeroLevel-1))

I recommend reading the fan manual, which includes what the abilities scale with and on page 240 it gives the full set of equations.

Doing a bit of research into the mechanics of the game, and spending a great deal of time trying to actually find this ability in a list of player or faction abilities, I found that Tsunami is a reputation ability that upgrades as you earn tear points for a mage class. I found a user on here asking about this mechanic, if the response to that question provides any additional help.

I also found this clever little web app that mimics the skill progression. Not only should it give you a little more detail on all available spells and abilities, but it acts as a helpful hero planner, so you can build your hero up as you wish, and get a better idea on how you should progress / what level you need to get too.