Reinforcement Magic:

A fundamental yet profound magic type that in its most prominent form's explicitly accessible to the higher tier and up characters. This magic type is used predominantly to enhance and elevate a mages own body and his/her abilities and it is what really accounts for the uncanny physical feats that are present in BC.

Instances of its use:

Reinforcemen Magic, Mana Skin:

As previously mentioned, most of the uncanny physical feat present throughout the series is particularly due to a combination of reinforcement magic and sensory magic. But, interestingly enough this situation also extends beyond the guise of what's simply physical!?

The concept of reinforcement magic and its variation can also be said to account for the feats of resistance that are present throughout the manga.

KI:

One of Yami's signature and most important abilities Ki works similarly to observation Haki. Ki is a bodily energy that all people have and give off whenever they do an action. Yami has learned to read Ki to sense things around him as well as sense his opponents intentions and read his movements allowing Yami to avoid and deflect attacks as well as sense sneak attack and environmental damage.

Yami can manipulate darkness both casually as well as form spells. The first import factor here is the fact that his darkness can damage light.

Licht mentions this in his statement here. This will be important as it shows Yami can damage Kizaru even if he transforms into light. To use One Piece terms he has an elemental advantage like Akainu vs Ace or Luffy vs Enel.

Yami has a few notable spells here firstly there is his avidya slash.

This is basically a thrown slash of darkness that Yami launches at his opponent. He also has the ability to create mini black holes which not only can be used to absorb attacks but also can stun opponents if they get into close to mid range. The other attack he uses in this scan is black blade which extends the range of his sword using darkness allowing him to strike from further distances.

Lastly,there is Dimensional Slicer an attack that can casually cut through dimensions. In these scan we see Yami escape from a space shield using this attack as well as slice straight through an insanely powerful opponent as Yami stats this attack is so dangerous because it doesn't cut opponents but instead cuts the dimension itself.

Yami is very fast notably being able to keep up with lightspeed opponents making him around lightspeed himself.

As far as destruction capability is concerned Yami has some pretty good statements behind him.

The captains were said to be capable of destroying the clover kingdom palace in a fight which is pretty impressive considering the palace is the size of multiple city blocks.

Yami is also pretty notable in that it is said that in a fight with another captain they destroyed a mountain.