You can’t use drucraft without a sigl.
If Euler’s Limit covers the creation of sigls, the Primal Limit covers why sigls are important. Simply put, no sigls means no drucraft.
New drucrafters generally find the Primal Limit the most confusing of the five. After all, the three disciplines – sensing, channelling, and shaping – are the foundation of drucraft, and you obviously can use all three of those without a sigl. If you couldn’t, it would create a chicken-and-egg situation – if you can’t use drucraft without a sigl, where do the sigls come from in the first place?
This confusion can be resolved by drawing a distinction between foundational drucraft and practical drucraft.
Foundational and Practical Drucraft
Foundational drucraft covers the fundamental skills necessary to become a drucrafter, which mostly (but not entirely) consists of the three disciplines: sensing, channelling, and shaping. They give the ability to detect and manipulate essentia, to understand and operate sigls, and to create sigls for the use of oneself or another. Although these skills are what differentiate a drucrafter from a non-drucrafter, they are not, in and of themselves, very useful. Without sigls, the study of drucraft would be considered a rather niche and esoteric field of little applicability.
Practical drucraft covers the working effects that drucrafters with access to sigls can produce. These are the things that people think of when they hear “drucraft” or “magic”: flight, invisibility, superhuman strength and endurance, the manipulation of space and time. They are the “finished product” of the art.
When the Primal Limit states that drucraft cannot be used without a sigl, it is referring to practical drucraft. Technically speaking, as long as you restrict yourself to foundational drucraft, you can use drucraft without a sigl just fine. It’s just that it’s not much use. And since most drucrafters want to be able to do things of use, then “you can’t use drucraft without a sigl” is, for practical purposes, almost always true.
Workarounds
The one big exception to the Primal Limit is in the name. Primal drucraft, for whatever reason, can be performed without a sigl . . . though note that just because something can be done, that doesn’t mean it can be done in a way that’s effective or useful.
The question of why Primal effects don’t require a sigl is one that has interested drucraft researchers for some time . . . after all, if they could figure it out for Primal effects, it might be possible to find out a way to use the other branches without a sigl, too. At the moment, the generally accepted theory is that the Primal branch can be used without a sigl because Primal essentia is pure and undifferentiated; drucrafters can use it because the skills to use Primal essentia overlap significantly with those required to manipulate their personal essentia via channelling or shaping. Beyond this, opinion diverges: some argue that Primal effects are inherently different to the other branches, and thus using effects from the other branches is impossible. Adherents to this theory sometimes go on to argue that, because of this, Primal drucraft shouldn’t be considered a “real” branch of drucraft, in the same way that “white” shouldn’t be considered a real colour, and that there should be only five branches, not six. This is a minority view, however.
Others who have studied the subject believe that the difference between Primal drucraft and the other five branches is a matter of complexity, not anything fundamental, and that theoretically, a drucrafter with a strong enough affinity and sufficient training should be able to use, say, a Light or Matter effect without a sigl. However, just because something is theoretically possible doesn’t mean that it can be done in practice, and it’s worth noting that, as far as is currently known, all attempts to accomplish this particular goal have failed.
Primal Drucraft: Assisted vs Unassisted
Primal drucraft is thus the only branch of drucraft where the same effect can be performed both with a sigl, and without. Both have advantages and disadvantages.
The biggest benefit to using a Primal sigl is amplification; a drucrafter using a Primal sigl can output vastly more power than one producing the same effect unaided. Using a sigl is also much easier; while creating a Primal effect unaided requires a solid fundamental grasp of the spell, any minimally competent channeller can use a basic sigl without any real understanding of how it works.
However, working through a sigl also comes with a cost in terms of fine control and feedback. No sigl, however well-crafted, can match the sensitivity of a drucrafter’s personal essentia, in the same way that no tool is ever quite a substitute for a human hand. As such, in areas where precision and delicacy are a priority, such as anything involving Wells, many drucrafters still prefer to work without a sigl where possible . . . though many don’t have the skill to do so in the first place.