2020-2-12  Black soul gems are essentially grand soul gems that can trap or store the souls of humanoid (player) races. If you dont have an empty black soul gem in your inventory when you kill a humanoid NPC (like a bandit or imperial soldier) that you have applied the soul trap effect on, you get the 'you don't have a soul gem in your inventory capable of holding such a soul' (or equivallent) message. Use an Enchanted weapon with 'soul trap' Or cast the spell 'Soul Trap' on a human target. The Evil who created Black Soul Gems will only take the Soul of a human. Animals are captured by the other Gems. You only have a listed number of seconds to make the kill after the hit is made.

If you want to get Enchanting up, activate the Mage Stone, smith a whole bunch of enchantable items, buy STACKS AND STACKS of small soul gems (Filled or empty makes no difference, but empty gems are cheaper) and enchant a weapon of yours with Soul Trap (onesecond) using a Black/Grand Gem.Having the Black Star will help here, it's reusable and you can kill Bandits/whatever to fill that to recharge your Soul Trap weapon.Then, fill the other gems you have using your new Soul Trap weapon. Once you've filled plenty, either use them or stack them at home and repeat the process. Once you've got plenty, enchant all the weapons or armour you made/bought and watch the skill goup.Consider also sleeping at a bed for that bonus too.

I've also found several Black Soul Gems off of Giants. But unless you're able to snipe them then that can be a hassle.I also heard somewhere that the dungeons rest every 40 game days or something like that.

(Not exactly sure, and haven't really been paying attention to the date in the game) If so then Illinata's Deep, the old ruin thing by the Lady Stone would be an excellent place to collect them. When I went through it for the quest, I found at least 3 since it's crawling with Necromancers.I also find them off of vampires usually, but be sure to bring lots of Cure Disease potions if you don't want to turn into one.

Go to the college of winterhold. Once you enter the courtyard there is a door on your left called 'Hall of Attainment' go inside. Travel directly across the room to the stairwell and go up the stairs to the next level. Once you on the next floor go into the first room on the left. This is Enthir's room. He sells and buys stolen goods. He has an empty black soul gem.Once you have purchased it you can exit out to the courtyard, then wait 48 hrs and you can go up to his room again and he will have another one that you can buy.

Just repeat the process until you have as many as you need.Also remember to bring a pickaxe with you when you go on the mission in BlackReach. In there you have a lot of mining to do and you will get a ton of soul gems of every kind. So far the best place I've found is the guy in The Colledge of Winterhold, but you have to join the Thieve Guild (I think) first. Other then that, as you lvl up, you'll start finding them more and more through raiding the dougens (forgive the spelling please) But I'm' still trying to figure it out how to acquire a lot of them, I remember back in Oblivion, there was a a casket or whatever you would place Grand Soul gems and after one night pass, they'll turn black. But just keep raiding doungens and lairs, you'll come across them.

Also, htere's a quest, Azura's Shrine, two ways to complete that, one way: be the rightguess player and have it turn tnto a reuseable Grand Soul Gem, or be like me and keep it a Black reusable Soul Gem. I think you have to be a level 5(five) to get this quest and that's by asking about rumors in the Inns or pubs.