It happens in the towers of time mode. You can choose consumables and assists to help you get through them.

the assists could be hinting at a yet to be revealed tag mode. But, that’s speculation on my part.

There are alos consumables that borrow moves from characters. The ones I saw were:

Reptile forceball

Cyrax's net

Rain's bubble

Shinnok's hand flick.

In MKX there was a similar thing but they were not consumables and they were from characters that were not playable. I honestly think none of those four will be playable.