Sasuke's Curse Seal vs Boruto's Karma Seal
Sasuke's Curse Seal by Orochimaru is same As Boruto's Karma Seal by Momoshiki Remember when Sasuke was fighting against Itachi. Itachi makes Sasuke to consumed all of his chakra. This is when curse seal true nature came in front of us. Curse Seals purpose is Hostile Take-over of hosts body. So its like injecting sperm, and make the Sperm grow by absorbing hosts chakra. When Host is completely out of Chakra or energy, His body is Mutated with Sperms injected. Its like Snake Bite. So the mark is always there. The mark(Karma Seal or Curse mark) has stored elements/memory of the ejector. The elements of the ejector acts as last supply of energy.When this store of energy is used by host, the ejector sperm(having memory) spreads all over the host body beginning of hostile take-over. When the Absorbing of the Chakra is at an extent that the ejector's sperms are totally grown into ejector. We can see how Orochimaru came out of Sasuke during Sasuke vs Itachi fight