After the first Sorcerer Supreme used the Time Stone, the Masters of the Mystic Arts assessed the threat level of the Infinity Stones and monitored them either through magic or spies.
The Infinity War prequel comic goes on to confirm that the Space Stone is inside the Tesseract.
Marvel Comics has released the second and final issue in their Infinity War prequel series and it sheds more light on the Infinity Stones, confirming the locations of some, while further teasing the mystery of the Soul Stone.
The new Infinity War prequel comic mostly focuses on a conversation between Doctor Strange and Kamar-Taj’s librarian, Wong.