What divine attribute is revealed in the phrase "God was, is, and is to come," in contrast to the devil who "was, is not, and is to come"?

Revelation 1:8 and 4:8 describe God as the one "*who was, and is, and is to come*", a phrase emphasizing His eternal nature and unchanging presence across time. In contrast, Revelation 17:8 speaks of the beast (often interpreted as representing the devil or a satanic figure), saying it "*was, and is not, and is to come,*" which appears to mimic God’s description but with a distorted twist. **What attribute of God is being emphasized through this triadic formula?** And how does the similar but corrupted version applied to the beast expose the devil's nature as unstable, temporal, or counterfeit? Is this a deliberate contrast showing God's immutability and sovereignty versus the devil's impermanence or false imitation of divine authority?