28:16 By the multitude of thy merchandise they have filled the midst of thee with violence, and thou hast sinned: therefore I will cast thee as profane out of the mountain of God: and I will destroy thee, O covering cherub, from the midst of the stones of fire.
28:17 Thine heart was lifted up because of thy beauty, thou hast corrupted thy wisdom by reason of thy brightness: I will cast thee to the ground, I will lay thee before kings, that they may behold thee.
and Isaiah 14
14:12 How art thou fallen from heaven, O Lucifer, son of the morning ! how art thou cut down to the ground, which didst weaken the nations!
14:13 For thou hast said in thine heart, I will ascend into heaven, I will exalt my throne above the stars of God: I will sit also upon the mount of the congregation, in the sides of the north:
14:14 I will ascend above the heights of the clouds; I will be like the most High.
14:15 Yet thou shalt be brought down to hell, to the sides of the pit.
20:2 And he laid hold on the dragon, that old serpent, which is the Devil, and Satan, and bound him a thousand years,
Other verses describe Satan as the destroyer going about upon the earth like a lion seeking those whom he can devour.
Eze 28 refers to the overthrow of the king of Tyre. Isa 14 (in Hebrew) talks about the Babylonian god Helel who is associated with Venus, the morning star, dawn/light. There is no connection in either of your quotes to the OT Satan, whom Judaism considers a faithful servant of God with no powers of his own.
In Greek the verse calls him fwsforoV that is phosphoros (i.e. the one who shines, light-bearer, morning star), which +Jerome translated into the Vulgate as Lucifer (from the Latin word lux for light).
It is only in the NT that the Christians are being introduced to the concept that Satan and Lucifer/devil are one and the same. This connection apparently existed in some common classes among 1st century Jews, and is mentioned in various books which are not part of the Pharisaical Hebrew OT. However, the concept does appear in OT Septuagint, which is the source used for most (over 90 percent) of OT verses quoted in the NT by the Apostles.
Because the Apostles treated Septuagint as Scripture, the Church included those books in the Christian canon. Martin Luther threw them out and accepted the Pharisaical OT of the Christ-denying rabbis of Jamnia, which the Protestants use to this day.