The exact damage formulas are not spelled out in game because there are a ton of factors which affect damage. There is an early Wiki for the game which I've been adding to a little bit at a time, with the help of other players:

tangledeep.wikia.com/wiki/Tangledeep_Wiki

I'm happy to explain the mechanics if you want to get down to the nitty-gritty of it :-)

1. Equipment Weapon Power. The display value of weapon power is 10x the actual value. This is because it felt better and more impactful to me to display a weapon with "175" power vs "17.5". Likewise, going from "18.1" to "18.9" power is kinda lame, whereas 181 -> 189 feels like more of a difference.

2. Character Weapon Power. This calculated value takes into account your level and stats. The formula is:

((Equipment Power) + (Equipment Power * Strength%) + (Level*2)) * (1 + 0.05*Level)

To plug in some numbers, say you have a weapon with power 200 (actually 20 under-the-hood), you have 40 Strength, and you're level 2.

20 + (20 * 0.4) + (2*2) = 32 * (1 + 0.05*2) = 35.2

The same weapon wielded at level 7 would have the result:

20 + (20 * 0.4) + (7*2) = 32 * (1 + 0.05*7) = 56.7

When an ability scales on "Weapon Power" it is scaling on this number.

3. Randomness. All attacks and abilities have a small-ish degree of randomness, about -15% to 15% of the calculated damage amount.

4. Other modifiers. Some creatures have resistances (or weaknesses) to specific elements. The Monster Corral can provide bonuses. Status buffs/debuffs can as well, plus blocking and crits, or bonuses to elemental damage that you have from gear.

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So in brief, Strength is basically a % modifier on your melee damage, but it ends up not being exactly 1:1 due to the influence of your character level. In terms of defense, as of right now, Strength gives you 0.2% physical resistance per point. In the next patch this may change slightly.