When an Arcanist formulates their spells they weave raw magic into a lattice of rituals, words, symbols, objects, gestures and materials. If they fail to execute the casting properly, the raw magic can release in a violent and destructive backlash impacting not only the Arcanist but also those close to them.
When an Arcanist casts a spell, if the Casting Test is a critical failure (all dice roll one), the energy from the spell explodes doing one point of force blast damage. The caster, being the source of the blast, always takes the damage. Bystanders in the Close range can make a Save Test to avoid the damage.
This is why Arcanist Novices must complete their training before embarking on independent or unsupervised projects.
The number of run away, rogue or outcast Arcanists contributes to the general perception of all Arcanists being dangerous. Within the Arcanist ranks are particularly talented members, Stewards, tasked with tracking and capturing or eliminating rogue practitioners.