So I am trying to get my sword of night and flame upgraded to level 10, which requires an Somber Ancient Dragon Smithing Stone. In order to get this stone, you must complete the Latenna questline, which means you must kill the Castle Sol boss Commander Niall.
This boss is insanely difficult initially. You have to try a lot of things and do a lot of research. After doing the homework, it does get a lot easier. Firstly, at the start of the fight, he will summon two knights to help him. These knights do a lot of damage, so you have to get rid of the knights first before tackling the boss.
One of the knights will run at you (the one that is dual weilding). This is good because that means you get a bit of time to kill him before the other two bosses reach you as well. Use a carian greatsword spell to quickly finish the first knight.
If the second knight charges at you, use a carian greatsword to finish him off too. If he doesn't, run far away from both the knight and commander Niall, and use a ranged spell (in my case I am using Comet Azur) to finish the second knight.
When Niall is the only one left standing, that's when I summoned my spirit to help. Mimic Tear will create an identical version of yourself. In this case since I have only equipped two spells, the mimic tear should shoot Comet Azur at commander Niall a few times. This will help a little bit but not too much.
The only way to defeat Niall is to know when to dodge, so his attacks don't touch you. If you get used to his attacks, you basically know when to dodge (at the last split second when he charges at you).
After you master the dodging, it'll simply be a case of standing as far away from him as possible, drink your mana potions and fire the Comet Azur. Hold down the comet Azur spell button so it will damage him as much as possible per shot.
Hope you can see how I defeated him and do the same!
