If we have guardian angels do we also have an assigned demon?
The short answer is: Possibly.
Some church denominations believe in the existence of Guardian Angels such as Catholicism, Eastern Orthodox, Anglicanism, Lutheranism and so on.
A guardian angel is an angel that is assigned to protect and guide a particular person, group, kingdom, or country. Belief in guardian angels can be traced throughout all antiquity.
In the books of the Hebrew Bible and Old Testament
In Genesis 18-19, angels not only acted as the executors of God's wrath against the cities of the plain, but they delivered Lot from danger; in Exodus 32:34, God said to Moses: "my angel shall go before thee." At a much later period, we have the story of Tobias, which might serve for a commentary on the words of Psalm 91:11: "For He will command His angels concerning you to guard you in all your ways;" (Cf. Psalm 33:8 and 34:5)
The belief that angels can be guides and intercessors for men can be found in Job 33:23-6, and in Daniel 10:13 angels seem to be assigned to certain countries. In this latter case, the "prince of the kingdom of Persia" contends with Gabriel. The same verse mentions "Michael, one of the chief princes".
In the New Testament the concept of guardian angel may be noted. Angels are everywhere the intermediaries between God and man; and Christ set a seal upon the Old Testament teaching: "See that you despise not one of these little ones: for I say to you, that their angels in heaven always see the face of my Father who is in heaven." (Matthew 18:10).
Other examples in the New Testament are the angel who succoured Christ in the garden, and the angel who delivered St. Peter from prison. In Acts 12:12-15, after Peter had been escorted out of prison by an angel, he went to the home of "Mary the mother of John, also called Mark". The servant girl, Rhoda, recognized his voice and ran back to tell the group that Peter was there. However, the group replied: "It must be his angel"' (12:15). With this scriptural sanction, Peter's angel was the most commonly depicted guardian angel in art, and was normally shown in images of the subject, most famously Raphael's fresco of the Deliverance of Saint Peter in the Vatican.
Hebrews 1:14 says: "Are they not all ministering spirits, sent to minister for them, who shall receive the inheritance of salvation?" In this view, the function of the guardian angel is to lead people to the Kingdom of Heaven.
As we can see, Guardian Angels is part of the faith in some churches. However there seems little to no information as to whether or not we have a counterpart of a Guardian Angel (Assigned Personal Tempter) at our side also.
While in the seminary (Catholic) most of the professors (all priests) believed that the possibility does exist, but the Church has not pronounced on this subject. My guess is that the Catholic Church will never pronounce definitively on this issue.
Sometimes we visualize moral decision-making as a debate between a bad angel whispering in one ear and a good angel speaking wisely in the other. There is a truth to this: according to St. Thomas Aquinas, one of the roles of the guardian angels is to fight off demons (Summa Theologica, Part 1, Question 113, Articles 2-6).
Guardian angels generally protect us from both spiritual and physical harm, according to Aquinas (Question 113, Article 5, Reply 3). This belief is rooted in Scripture. For example, Psalm 91:11-12 declares, “For he commands his angels with regard to you, to guard you wherever you go. With their hands they shall support you, lest you strike your foot against a stone.” - The 20 Things Guardian Angels Do for Us
The main reason why I believe the Catholic Church will not confirm the believe that we are assigned a Personal Tempter, even if true (as I believe) is a question of jurisdiction. Here is a little antidote story to show what I mean.
The Last Judgement, painted from 1535 to 1541, covers the entire altar wall of the Sistine Chapel. It depicts the second coming of Christ on Judgement Day, surrounded by apostles, disciples, saints, martyrs, angels, demons, the saved ascending to paradise and the damned being dragged to hell. It’s an extraordinarily complex and detailed scene, especially given the enormous size of the fresco. Painted twenty-five years after the completion of the Sistine Chapel ceiling, The Last Judgement is the work of the mature Michelangelo, at the peak of his artistic powers.
The work had been commissioned by the Pope, but many Catholics felt that The Last Judgement was inappropriate for a place as sacred as the Pope’s private chapel. The Papal Master of Ceremonies, Biagio da Cesena, deemed the fresco outrageous, and more suitable for public baths or taverns than a chapel. “….it was mostly disgraceful that in so sacred a place there should have been depicted all those nude figures, exposing themselves so shamefully”. Michelangelo responded by making Minos, judge of the underworld, resemble Cesena. It’s an extremely unflattering portrait; Minos/Cesena has the ears of a donkey and a snake biting his genitals. When Cesena complained to the Pope, the Pope reportedly pointed out that his authority did not extend to hell. The painting remained unchanged. - Nudity and controversy in the Sistine Chapel: the revolutionary ideas of Michelangelo
Minos, god of the underworld, with the face of Biagio!
So if Satan assigns a Temper to each individual that is his prerogative. It may be common to believe so. But the Church does not know for sure, so she can not make any positive affirmations one way or another. Popular culture seems to believe it is so.
In the book, The Shepherd of Hermas, of around A.D. 140–150 has a reference to the idea of two angels:
The non-canonical early Christian book, The Shepherd of Hermas, of around A.D. 140–150,1 has a reference to the idea of two angels: "There are two angels with a man—one of righteousness, and the other of iniquity". These angels in turn descend into a person's heart, and attempt to guide a person's emotions. Hermas is told to understand both angels, but to only trust the Angel of Righteousness. The concept is similar to ideas of personal tutelary spirits that are very common in many ancient and traditional cultures.
In some Christian folklore, each person has a dedicated guardian angel whose task is to follow the person and try to prevent them from coming to harm, both physical and moral. At the same time each person is assailed by devils, not usually considered as single and dedicated to a single person in the same way as the guardian angel, who try to tempt the person into sin. Both angels and devils are often regarded as having the ability to access the person's thoughts, and introduce ideas. - Shoulder angel
The idea of a shoulder angel is often used in iconography:
The shoulder angel often uses the iconography of a traditional angel, with wings, a robe, a halo, and sometimes a harp. The shoulder devil likewise usually looks like a traditional devil with reddish skin, horns, barbed tail, a pitchfork or, more precisely, a trident and in some cases, cloven hooves. Often, both resemble their host, though sometimes they will resemble other characters in the story who are responsible or mischievous. In Western culture the idea develops the Christian concept of a personal guardian angel, who was sometimes considered to be matched by a personal devil who countered the angel's efforts. Especially in popular medieval dramas, like the 15th century The Castle of Perseverance. In both this and Christopher Marlowe's play The Tragical History of Doctor Faustus, of about 1592, the "Good Angel" and "Bad Angel" offer competing advice (Act 2, scene 1, etc.) to the hero. - Shoulder angel
In writing about Guardian Angels, St. Thomas Aquinas does has this to say:
Man while in this state of life, is, as it were, on a road by which he should journey towards heaven. On this road man is threatened by many dangers both from within and from without, according to Psalm 141:4: "In this way wherein I walked, they have hidden a snare for me." And therefore as guardians are appointed for men who have to pass by an unsafe road, so an angel guardian is assigned to each man as long as he is a wayfarer. When, however, he arrives at the end of life he no longer has a guardian angel; but in the kingdom he will have an angel to reign with him, in hell a demon to punish him. - Whether angels are appointed to the guardianship of all men?