It was actual ink. Lin Jin's Cosmos Ink.
The Cosmos Ink was so phenomenal it could create a tunnel to travel through space via a painting realm. Since he received the ink from Shu Xiaolou, Lin Jin had continued to refine it until his mastery over the item was above Shu Xiaolou, the original creator. After separating it into two drops, one was given to Xiang Yun by placing it on the blood ghost's blood and the two ghost worms.
After refining the Cosmos Ink, they possessed the capability of linking up no matter where they were. Even here in the extraterritorial zone where the link to the painting realm was weakest, two drops of ink was more than enough to support teleportation.
Two options were made available to Lin Jin when he passed the Cosmos Ink to Xiang Yun. First, when Xiang Yun succeeds in locating Miao Yan Zhenren and the Mystery Dao Sect, Lin Jin could teleport them all here if the situation called for it.
