They do not have any functional purposes, they are simply decorative items. NPCs probably kept them because they look pretty, but you can't actually do anything with them.
It works the same as a black soul gem but it is reusable. The black soul gems ubsorb human souls.
Sawn log. Nails. Refined moonstone. Iron ingot. Grand soul gem (with grand soul). Gold ingot. Just need one of each.
GET soul gem and unlock the soul gems upgrade
That would most likely be black. However, There is no way to trap a dragon soul in a soul gem. They are impervious to soul trap of any kind even when using the restoration exploit. I don't want to explain further due to spoilers.
you find sunburns soul gem in his adventure packs level
Make sure you have any filled soul gem that is higher than a petty soul gem, go to your weapons, highlight the axe and press RB. That goes for any other enchanted weapon/armor. If you have the game for PC, it should tell you which button to push in your list of options that you can do with the weapon/armour.
In Skyrim you can either take them from a person you have killed or more commonly they are found as random loot, usually in caves where a lot of necromancers live. They can also be crafted with the lightning attractor in the Soul Cairn (Dawnguard DLC), can be found from geode veins in Blackreach and can be purchased from Enthir in Winterhold and Falion in Morthal.
Darklight krypt is where you find sunburns soul gem
yes your best bet is using a dark soul gem (grand) that should fill it up for ages also if you disenchant it you can put it on whatever weapon you like
Whirlwind's soul gem is on Chapter 17, Creepy Citadel. After the little goblin puzzle, there is a platform with two Gargantulas. Defeat them to open the gate and get the soul gem. Hope this helped.
Sorry I don't know but I know where Sunburns soul gem is it is in Dragon's Peak about 5 minutes into it lean of the island and there is a dragon waiting there to take u to his soul gem
you find the soul gem in darkwater cove but i dont know the exact place in the level