This depends a lot on your definition of mysticism but it wasn't unusual for European nobleman/clergy to have an active interest in astrology/astronomy. These disciplines were heavily intertwined together with religion, philosophy, mathematics, geometry, geography and medicine/alchemy.

Now the rediscovery of these scholarly traditions through contact with the Arab world in southern Iberia and Italy from the 11th century onward isn't the subject of your question so i'll just cover the essentials.

The conquest of Toledo in 1085 and the Norman conquest of Sicily between 1060 and 1091 gave European's direct access to many books which could now be more easily translated into Latin. This collection of ancient (mainly) Greek, with it connections to ancient Egyptian and Babylonian, and current Muslim, with it's connection to India, knowledge spread across west-European courts, monasteries and universities.

Adelard of Bath, Gerard of Cremona, Constatine the African, Abenzra are all famous translators/scholars of this knowledge and they, and others like them traveled far and wide to attain this knowledge.

This was a multicultural and multireligous affair. Adelard of Bath came from England to study in Sicily and other parts of the Mediterranean. Gerard of Cremona, from north italy, moved to Toledo, Constantine the African was a christian from lybia/tunis who moved to Italy. Abenzra, a spanish jew who travelled all over western-Europe, for example had Henry II as a patron and gave lectures in London and Oxford.

In these traditions these scholars sought answer's. Mystical explanations for why the world was, now although the rediscovery of these texts can't be underestimated it is important to note that their already were west-European christian scholars active in these fields in the early middle-ages.

Charlemagne at his court for example had the mathematician and theologian Alcuin of York (famous for the wolf, sheep, cabbage riddle) who taught Charlemagne and his heirs, about 'the harmony of the sky, the rising and setting of starts and the seven planets. He stayed active at the court for nearly a decade and a half, with a 2 year interlude. Afterwards he was made Abbot at Tours as a reward/retirement from court. From there he could still easily be summoned by the court for advice.

He was very influential, he was behind Charlemagne decision to abolish the death penalty for pagans in 797 for example.

Now due to the intertwined nature of all these different scholarly subjects it is difficult to answer your question. What we do know is that in medieval society there was an interest in searching for explanations and divination in the stars and planets and proof of the natural divine order. Astronomy, astrology, religion, geometry, mysticism, mathematics, philosophy were combined in many different ways to create a lens through which to understand this order.

Men would use this lens to guide their decisions. A doctor might consult the position of the moon whether to perform an operation. An astrologer can be consulted to consult the planets for an auspicious date for a wedding or coronation. A nobleman, looking to his advisor's, were all, in a lesser or greater amount influenced by this, very diverse, lens.

William of Conches, tutor of Henry II of England, for example his theory was that planets control nature and the human body. The planets heat up the atmosphere, which in turn heats up water, which is present in all life. Therefor the planets influence everything. Henry II would be intrigued by similar scholars, becoming a patron of the aforementioned Abenezra.

But perhaps an example; closer to my home, is the life of Willem van Gulik, the younger. (Also known as William of Jülich)

His mother was a daughter of Gwijde van Dampierre, count of Flanders. He studied in Bologna in 1300, to prepare for a life as clergy, where he became fascinated with astrology. He became rather influential and had several positions (in Liege, an important bishopric city)

During the Flemish revolt of 1297-1305, a war between the county of Flanders and the King of France, which I'm not gonna explain in details he became one of the more important commanders opposing the King. His love for astrology was well known and he even had a "magician" in his entourage, who was rumored to turn him invisible (and making him reckless).

He eventually died, after winning at the famous battle of Courtai in 1302 and Arke in 1303, in a failed attack in 1304 at Pevelenberg. The French king barely escaped but William and his followers were cut down. His body was never found though, so for some he became a mythical figure like King Arthur who would return in a time of need.

The magician was later convicted and broken on the wrack by Willem his cousin Jan II of Brabant.