Yes but do I need to keep 15 points to progress the tenebrium skill too? (like two handed or bow), or only with the skill 'unblocked' will be enough?
Tenebrium is new ability ... after doing a quest it gets added to your character sheet and all characters receive a +1 bonus. This bonus is not a hard point, this means after investing 15 points you get +6 tenebrium resulting in +60% damage with tenebrium enchanted weapons.
(For example, other comments on Steam says that the Tenebrium skill will stock with weapons skills, i.e. if I have Two Handed 3 and Tenebrium 1, I will have +4 bonus)...
Thats wrong - they don't stack ... for tenebrium enchanted weapons only the tenebrium skill is used. So if you have Two Handed 3 and Tenebrium 1, you will have only a +1 bonus.
some more tests:
Ability points are not as limited as it seems:
After collecting 5 stones (star stones and blood stones count) you unlock a vendor at homestead (Hall of Secrets), which sells a book which increases attribute points by 1 and a book which increases ability points by 3. You can rebuy these books every level-up. If you need every point, try to delay some side quests to reduce level-ups until you get all 5 stones in Cyseal.
Now i tested this - with a 2-handed-warrior and a mage (both lone wolf/leech, normal difficulty). Collecting the first 3 stones is easy (clinic, crime scene, road to silverglen). After this you are Level 3. Then i sneaked into black cove fighting my way to the bloodstone (try to avoid the fight with the orcs outside ... use scoundrels invisibility skill). This was interesting - you are Level 3/4 and enemies are Level 6. After defeating the ghost pirate you should be Level 5. Now go after Evelyn this should bring you to Level 6. Now sneak around the church and defeat Braccus Rex and collect your fifth stone to unlock Hall of Secrets. If you avoided enough fights you should still be Level 6. On my first playthrough i was already Level 10 by that point - this means 4 more Level-Ups resulting in 4 additional attribute points and 12 additional ability points from books. Not bad, but this is a very tough fight because Braccus Rex is Level 9. Using "Melee Precision Stance" or "Bless" on your warrior is mandatory. If it's to tough take one more Level. At Level 7 you can learn some important skills like Whirlwind and you have enough ability points accumulated (if lone wolf) to max men-at-arms and you are able to take "Weather the Storm". That should make everything a bit easier.
