This is the sixth part in an ongoing series about Earthdawn. Introduction and Index.
The information presented here has been updated for Earthdawn Fourth Edition (ED4). Most specific information for spellcasting in ED4 can be found here.
Spellcasters (also known as magicians) are a specific subset of adepts whom, unsurprisingly, cast spells. The core disciplines which are considered to be spellcasters are Elementalists, Illusionists, Nethermancers and Wizards. Spells are a specialized form of thread magic. The basic premise is to take energy from astral space (where magic comes from), pull it to our reality and form it into the pattern of your spell. The patterns for some spells are more complicated than others and may require you to weave one or more threads first. All of the spell patterns are temporary and dissipate after their effect is complete (there is an exception to this; a spell may be given a Name and changing it into an independent astral entity). Two talents are required at the very least, Spellcasting and Thread Weaving. Astral space is in such a state, however, that a spell matrix is highly recommended, but not strictly required.
Prior to the Scourge, spellcasting was performed without the need for a spell matrix. As Horrors began to arrive, their very presence polluted astral space, particularly in locations they resided. Exposure to corrupted magic pulled from astral space is dangerous to a magician in two ways: first it can cause damage to their pattern (manifesting as injuries), and second, perhaps most important, a Horror in the nearby area can notice the activity and take that opportunity to place their Mark upon the spellcaster. A Horror mark is bad news and will be part of a subsequent article; for now just take my word that an entity from beyond time and space which feeds only on your pain and suffering with a direct link to your being isn't something you want.
To solve this increasingly problematic issue, magicians created the spell matrix: essentially a magic filter, or firewall. Initially they were contained within thread items and filtered through that item's pattern, but after the Scourge a clever Nethermancer figured out how to use your own pattern as the filter and spell matrices became talents. There is a limit to the number of spell matrices your pattern can sustain, so thread items containing a spell matrix are still available and popular with magicians.
In general, a spell matrix can only contain one spell at a time (a Shared Matrix is the exception), and some varieties (Enhanced and Armored) also contain a single thread which is pre-woven. Changing spells within a spell matrix takes 10 minutes of meditation, though can be accomplished on the fly in times of need, at some cost in Strain. Casting can be performed without a spell matrix (this is referred to as "raw casting"), though there are associated dangers depending on the corruption of the area you are in (Astral Sight can reveal this). For example: an untouched kaer is likely pretty safe, but one that has been breached by a Horror is probably quite corrupted. Directly casting from a magician's grimoire (effectively a spellbook, but there is no requirement of it being a book) is also a possibility, but things going wrong can be rough on it (let's hope your tattoos aren't also where you keep your spells!).
The idea behind a spell matrix is to limit spellcasters' access to spells in times of stress (e.g. combat), but when time is not of the essence they will have complete access to all of their spells. Weaving threads generally takes a turn per thread, though failed rolls will make it take longer, or an exceptional roll, shorter. Additionally, all spells can benefit from additional threads beyond the requirements woven prior to casting. These can improve various aspects, depending on the spell, and the number of additional threads possible depends on the circle of the spellcaster. When a magician is not constrained by time, they have considerable resources, but when moments count, they have to make potentially difficult decisions about what tools are practical (e.g. how big of a "boom" do you need for the fight). As such, magicians have a more limited role in combat than many other fantasy games, between more powerful spells taking longer to cast and limited access to spells. This means disciplines obviously designed for combat (e.g. Swordmaster and Warrior) are front and center during those scenes; it is their time to shine.
Learning new spells requires the Patterncraft talent, along with time. A tutor will make this task easier, though with sufficient downtime it isn't an issue. Beyond starting spells, any additional spells have to be found, purchased, or earned.
It is hardly all doom and gloom for spellcasters. There are no limitations on the number of spells that can be cast per day, practical (through accumulating penalties) or otherwise (mana points). Many spells provide unique effects that cannot be replicated in any other way (a spell that allows you to relive a corpse's last moments of life). Magicians strongest suit is as a utility character. Outside of combat they can bring their full arsenal of spells to bear upon any task with no limitations. There are some utility spells that are simply amazing in what you can do with them.
Despite their limitations, spellcasters still bring elements to the table which other disciplines will not be able to until higher circles (if they can at all). Most opponents are more resistant to physical damage than mystical, at times to an amazing degree, meaning that the magical attacks a spellcaster can bring to the table will be invaluable. Magicians, if so inclined, can select an array of spells to target a variety of defenses with each type of damage, including spells with different thread requirements if speed or power is more important. The end result is that a magician, with the proper information and inclination, can contribute significantly to combat. It just ends up being a thinking game where you have to analyze the data and select the best response. As well, spellcasters have access to a number of control oriented combat spells to support the more conflict members of the group.
I really like how this ends up working. Everyone still gets to contribute meaningfully, but niche protection is maintained. The spellcasting system can be conceptually difficult at first and represents a major departure from how D&D tends to function, but it works magnificently and plays to many of the classical strengths of the fantasy magician in older school games. There is debate how true that remains at higher circles, though the limitations on finding new spells, which get downright rare as the circle increases, can significantly mitigate that. The fact that finding old, lost spells is an adventure unto itself excites me. It plays with the post-apocalyptic and exploration themes, and gives any group reasons to continually search out dangerous and forbidden areas, to start messing around with the upper echelons of power and make deals with dragons.