1) Pure Rage is my favorite skill. Not only because it gives you the second level of Blood Wrath from the start (along with the other perks that the Barbarian will have acquired by then), but also because it's not that disadvantageous to acquire, using the skill wheel.
2) Urgash's Call is a very good skill. It's very useful and effective in battle. I've used it many times, and it's helped me out more than once.
3) Relentless Force is not a very good skill. You can only apply Guard to one of your units, and it's not a given that they will be the ones attacked. Besides, I think this skill was invented just to end a battle in a draw by applying Guard to the last survivor and attacking all the attackers with tripled damage. Of course, skills for achieving absolute mastery are very good, for example, Guardian Angel or Fight to the Last, BUT I think there are more drawbacks. I agree with those who say that Knights are stylish enough without a skill, and even more so when they acquire strong Paladins; I won't even comment on that. In general, I think this skill exists only to somehow create a balance between the races.
4) Howl of Terror is a pretty good skill. But the first thing I didn't like about it is that you can't get the Mentorship skill, which is very useful for long battles. Secondly, I really didn't know that - morale, no matter how high, only reduces the chance of a turn to 60%. If that's the case, then this skill is only beneficial with negative luck. It also follows that it's not very beneficial against Elves. In general, this skill is only useful when fighting races that rely on their army.
5) True Luck and Absolute Defense - I decided to combine these two skills because they are mutually opposite, and if (God forbid!) players with these two skills meet, then the heroes will have to rely only on their already acquired skills, army, etc., because these two absolute skills will cancel each other out and be useless. This is the main thing I want to emphasize. And if you consider them separately, then Elven Luck is very good, but as other forum users have noted, Elves with their already high luck will not benefit much from sacrificing good skills for a very difficult-to-achieve skill (unless they are fighting Necromancers with their artifacts and skills that reduce luck). Therefore, I rate Elven Luck as not a very useful thing. But I rate Absolute Defense a little higher, because the ability to deprive luck and even give bad luck will be useful in any battle, no matter who your opponent is (again, I repeat that Elves are the exception). You will have to sacrifice something, but I think that this sacrifice will be beneficial. That's why I think the Gnome skill is quite useful.
6) Fury of the Elements - I've already tried this ability, but it didn't impress me much. Of course, it has some benefits, but for some reason, it seemed less beneficial to me than, for example, Elven Luck. I don't often play as Warlocks; I prefer large numbers and brute force, like Orcs. Therefore, I can't guarantee it, but it seems to me that Fury of the Elements is not a very powerful skill.
7) And finally, the last skill - Arcane Knowledge. First, I agree with those who say that knowing all the spells is not very good, because you can't use them. BUT, what if you don't get the spell you need, no matter how hard you try? Besides, learning all four schools of magic to know all the spells is not very beneficial. Of course, some only learn two, sometimes three schools, but the race is called Magic, it should know everything and cast spells better than the others (except for Warlocks, they are unmatched in spellcasting, as far as I know). Therefore, I think this is a very useful skill, and it also intersects with my favorite Mentorship and is achieved in only 24 levels (under ideal conditions).
And the general conclusion is that everyone here has already expressed all sorts of pros and cons of all the absolute skills, but, of course, each of them can be useful. For some maps, they are not needed, for some, they are essential; I personally always try to get the skill, even if it harms me later. But as soon as I finally get it, I get a good advantage and a chance to defeat even a very strong opponent. If I have missed something here, please don't correct me or argue. I have expressed my opinion, and I will not back down from it.
Ugh, this is the first time I've written such a long message.