Arcana

Willpower has incredible force when used in the right way. Humans especially can force reality if they put enough effort into it. Of course, every attempt to do so risk making the Thorns grow around you. The way around this is to use principles employed by the willpower of many before you. The reason astrology can be used for divination is that it has been used like that for thousands of years. Every time it has been practised has added to make it natural and accepted by the Thicket.   Building power to create an effect doesn't happen in one quick motion. Any attempt requires a full ritual and most results, while potentially very powerful, are subtle when seen by mundane people. However, those who know what they're doing can accomplish feats that shake worlds. Sometimes literally.  

Branches

There are many different words used to describe the different ways one can influence reality. Those familiar with the Thicket of Thorns often refer to them as Branches, imagining them as the result of the Thicket growing between worlds. Each of them still needs to be channelled through a tradition to be useful and pulling too much on any branch increases the risk of being pierced by the Thorns.   Even humans rarely gain control over more than two or three branches, but that can be enough to wreak havoc on the world. Careless, selfish, or outright malicious use has created catastrophes, mass hysteria, or widespread death. and the arcane practitioner is often the first victim.

Traditions

Attempting to manipulate reality without any framework at all is nearly impossible. Most beings have naturally developed ways to pull on the branches in very specific ways, but that isn't very versatile. Advanced practitioners use collective belief and established methods to achieve what they want. Enough people believe that crystals can heal that they can use to move a Death Branch away from a person.   A tradition, despite its name, doesn't have to be very old as long as enough people believe it possible. A physics experiment to measure quantum tunnelling can be used with a Space Branch to achieve a teleportation effect. That said, older traditions are often easier to use. It requires an advanced sensory deprivation tank to reach the same connection with the Astral Plane through technology as it would take the right herbs to do it via traditional shamanism.