- A reference guide and manual in Russian for Heroes 3.

I was actually interested in the general formula. That is, what the final damage consists of and how.
Using your example with hydras:
- is the damage determined randomly (RND) within the range of 15-30, or, which I doubt, does it depend on some other factors?;
- if the damage is 20, will luck and double damage also add 20, or will the computer again randomly choose a value within the range of 15-30?

The base damage is determined through RND within a delta (except for the situation with the blessing, when the base damage is equal to max or max+1), then this damage is used in the formula several times, but it no longer changes, i.e., it is one and strictly fixed for each round of combat. The secondary skill "Attack" adds a portion of the base damage to the total damage, depending on the level of development of this skill. In turn, the specialization "Attack" (Crag Hack) modifies not the damage directly, but the value of the secondary skill... The attack/defense modifier changes the amount within the range of (-0.7...+3.0) of the base damage... Luck adds the value of the base damage to the total... :)

It's all quite confusing at first glance, but I think it can be broken down quite clearly with a specific example... Let's take an example (what unit is fighting against what unit, who is our hero, what is the terrain, what are the primary skills of our hero and the enemy hero, do we have "Attack" among the skills, does the enemy hero have "Armor" and what is its level of development, etc.). After all, the formula is multi-step, and the calculation will be different in each specific case...