Dark Ages

If no other worldview is chosen, the "Philosopher" skill is free.

But the Philosopher skill is already free. Or does it refer to "Teacher"?

Devoted Weapon

Does it stack with weapon skills? For example, together with the polearm skill, does it give +2 range and a double preemptive strike?

Monotheism [-]

It's probably too early to judge, but it looks a bit overpowered: it costs nothing, doubles one of the stats, gives a number of useful defenses, and +25% skill points. It's a very versatile bonus.
Even "Terraform," at best, gives +2 skill points (and only if you take a specific skill) and a situational ability. The ability (for which you still have to pay) to kill one NPC once a day doesn't seem very useful from my perspective, unless it allows you to one-shot even very strong opponents.
The situation with "Darkness" is more complicated. But the basic skill looks quite unique and won't suit every character. "Servant" will give equivalent bonuses to "Monotheism," but for a price and with a restriction on the character's freedom. And without a discount on skills. In other words, for 2 points and less freedom of action, the player will get a weaker version of "Monotheism." But "Dark Magic" looks quite good (better than "Power of the Ancients"), although I'm not sure if the lower cost of 1 point is equivalent to the lack of bonuses to stats.
Nothing is clear about "Philosopher" yet. It all depends on how large the bonus to stats will be. But something tells me that it's less than +100% to concentration. And "Monotheism" will also give additional skill points, which will allow you to increase other stats (possibly even more than a Philosopher can). However, "Teacher" looks like a useful skill (although it all depends on how randomly the companion is generated).