13:1 And he stood on the sand of the seashore. And I saw a beast coming up out of the sea, having ten horns and seven heads, and on his horns were ten diadems, and on his heads were blasphemous names.
And he stood on the sand of the seashore.
This sentence according to the best old manuscripts belongs with the last verse of the previous chapter. The devil is contemplating his next move.
And I saw a BEAST coming up out of the SEA,
While this may be a literal sea creature ugly as it is described, the most likely interpretation is that a demonic leader will come up from the "container of evil spirits", the SEA. The description of SEA in Revelation 17:15 would also indicate that the SEA means someone from among the world's nations.
The ten horns may be the ten toes in Daniel 2:36-45 and thus are ten kingdoms. Much has been said which countries these kingdoms may be. It probably will not be revealed until the tribulation time which of the then existing nations make up the 10 countries. Since the Bible is an "Abraham book", one would think these are from Abraham's seed. Thus, the 10 nations most likely are those with a majority of "Ishmael peoples".
Symbolically, the seven heads may be seven demonic realms. Each country has its own culture where the country is known for some social value (or lack thereof). There is a list of evil realms in Revelation 21:8 which may define these demonic realms. Contrast this SEA BEAST (counterpart of Christ) to what Christ is.
The ten nations will have someone in authority with special demonic powers. These do not necessarily have to be political leaders. they could be spiritual (Hebrews 5:7-10), economic (1 Timothy 6:10), or judicial (Luke 6:37-38).
This prominent feature shows up again in Revelation 17:3. There the sea beast is scarlet and still spouting off those BLASPHEMOUS names.
Note that the devil has a thing for NAMES. If you are looking for a build up of your pride, someone has to know your name to brag about you. Apparently it is very irritating to the devil that OVERCOMERS (Revelation 2:17) have a name which no one knows, the 144,000 have a name on their foreheads (Revelation 14:1) known to Jesus and the Father, and the Book of Life contains the names of people the devil cannot get to (Revelation 3:5).