Mortal Kombat 11's Krypt is massive. In various over- and underground areas there are Chests, Soul Vaults and Ghost Chests that can be opened for Koins, Soul Fragments or Hearts.
Koins can be earned in fights, completing tutorials, opening chests or new areas in the Krypt.
Soul Fragments can be earned in fights, found in chests or earned by killing people in the ghost realm.
Hearts can be earned in fights, found in chests or earned from bodies / monsters in the Krypt.
Inside the Krypt, there are standard chests (numbered in YELLOW on the maps). Most of them open up with Koins, some of them with hearts. The fire chests have to be unlocked first, by finding a burning skull head and destroy it with Scorpion's chained Spear that can be found in the Krypt.
Then there are glowing people or items. Those can be interacted with when Ermac's Amulet was found in the Krypt. Those Vaults are numbered in GREEN on the maps.
After finding Kenshi's Blindfold, you can also enter a ghost realm. Here, you can find some chests too. They are numbered in BLUE on the map.