If you are going to open a 6-star hero crystal or saving to open one or many, you may want to know that what champions are currently available in the 6-star Basic Pool and the can compare against the featured heroes and decide which one you want to open.
The Cost or Required shards to Open 6-Star Heroes
Basic Pool Requires 10,000 shards
Premium Pool requires 15,000 shards
What Champions are Available in 6-Star Basic Heroes Pool and What Champions are Upcoming? Should I wait or Open my 6-star
Here is the List of Available Champions
There are some new champs that will be added to the basic pool on December 04, 2018, e.g. Wasp, Ghost, Red Skull, Heimdall, Korg, Masacre, etc.. So if you want them, you will have to wait and try your luck when they are added.
However, they have recently added, Iron Man Infinity War, Captain America Infinity War, Corvus Glaive, Domino, Sabretooth, Proxima Midnight etc.. those are much more powerful compared to the one they will add on December 04.