As an expert in the lore of fantasy and role-playing games, I can provide an answer to your question about the Black Soul Gem, which is a popular item in the "Elder Scrolls" series, particularly known from the game "The Elder Scrolls III: Morrowind."

In the game, the Black Soul Gem is used to trap the souls of creatures. The process of filling a Black Soul Gem involves capturing the soul of a creature by defeating it in combat and then using the gem to trap the soul. The soul trapped within the gem can then be used to enhance weapons, armor, or other items, effectively imbuing them with magical properties.

It's important to note that the Black Soul Gem is a unique item in the game, and it has a fixed capacity that cannot be increased. Once the gem is filled with one soul, it cannot hold another until the current soul is released or used.

Here's the answer in English:

"In the 'Elder Scrolls' series, a Black Soul Gem is filled by capturing the soul of a creature. This is done by defeating the creature in combat and then using the gem to trap its soul. The trapped soul can be used to enhance items with magical properties."

And now, the translation in Chinese:

"在《上古卷轴》系列中，黑魂石宝石通过捕获生物的灵魂来填充。这是通过在战斗中击败生物，然后使用宝石捕捉其灵魂来完成的。捕获的灵魂可以用来增强物品的魔法属性。"

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Taken from the Skyrim wiki: Black souls are those of sentient, humanoid beings such as Imperials, Argonians, Khajiit and Dremora, while white souls are those of animals and certain lesser Daedra. If you have the ability to make weapons with soul trap then just have an empty black soul gem and use the soul trap weapon.read more >>