These are claws similar to those of a cat that can absorb surrounding energy and use it to attack. (I.e. If the claws are used near a highly poisonous plant, that plant's potent energy will go to the claws and can possibly poison the target.) They appear to be actually apart of the user rather than being worn like a glove.
This energy likely came from Kori as he was near Yami when he used the claws. This energy gave the claws a slight freezing effect on the monster.
This energy likely came from a poisonous plant or animal in the vicinity when Yami used his claws. This poisoned the monster that Yami attacked.
- These are very similar to that of Wolverine from the X-Men.