Idle Heroes have a Myriad of Artifacts where each Artifact comes with its own unique stats and abilities. There is a grading of Artifacts done in the following manner:
Orange>Red>Green>Purple>Yellow>Blue
Artifacts which possess the same value of engulfing have the same cost for upgrading themselves. When there is a need to use a greater number of engulfing points, one needs to upgrade the Artifacts, which then converts all the redundant engulf points into Afterglows. 1 Afterglow=10 engulf points. However, you cannot upgrade or disassemble an Afterglow.