In almost every beginner class guide video I can hear about “using blood shards on certain Kanai’s cube legendaries” which can help during leveling or which can be value at fresh 70. Eg. “if you have shards left you can make Nemesis bracers” from a barb video.
Although I didnt make challenger cache (didn’t play last season) I have some shards from leveling. However I can spend them only at Kadala.
How do you use shards through cube?