13:6 It opened its mouth to blaspheme God, and to slander his name and his dwelling place and those who live in heaven.
It opened its MOUTH
This mouth is the one given to him in the previous verse
to blaspheme God,
This was the same accusation which lead to Christ's crucifixion (Matthew 9:3, Mark 14:53-65).
Jesus indicated that even blasphemy can be forgiven except for blasphemy against the Holy Spirit (Mark 3:28-30). Since the Holy Spirit is part of the triune God, the BLASPHEMY AGAINST GOD seals the "sea beast's" doom.
to SLANDER
His NAME encompasses all that is Christ from his humanness to the fulness of Deity (Colossians 2:8-15).
It is appropriate to refer to his DWELLING PLACE (1 Corinthians 3:16). Recall that “true believers” leave the earth either by physical death or by the “great ascension (the rapture event - 1 Thessalonians 4:12-18), that is, to go to his DWELLING PLACE”.
This is YOU if you DO NOT take the 'Mark of the Beast' and are NOT in 'the LIST' (Revelation 21:8)