Each incantation has its own consequences for failure (two failed skill checks in a row). In general, they can be divided into the following categories. Attack: A creature is called from elsewhere to battle the caster (and often any bystanders and secondary casters). The incantation’s description tells the GM what Challenge Rating the creature should have, how it behaves, and how long it persists.
Augment: The incantation was supposed to weaken or destroy its target, but it makes it more powerful instead. A damaging spell might heal its target or cause it to grow in size, for example.
Betrayal: The incantation seemingly succeeds, but the subject of the incantation (or in rare cases the caster) loses all allegiances and gains their opposites. In general, the subject now hates all it loved before the incantation. The subject may keep its new allegiances a secret. Whenever a character attempts an incantation with a chance of betrayal failure, the GM should make the relevant die rolls in secret.
Damage: The simplest consequence of failure, damage is dealt to the caster or the target, depending on the incantation.
Death: Someone—usually the caster or the target—dies. Depending on the incantation, a successful saving throw may avoid the effect of failure.
Delusion: The caster believes the incantation had the desired effect, but in fact it had no effect or a very different one.
Falsehood: Common with divinations, the incantation delivers false results to the caster, but the caster believes the results are true. Whenever a character attempts an incantation with a chance of falsehood failure, the GM should make the relevant die rolls in secret.
Hostile Spell: The caster of the incantation is targeted by a harmful spell or incantation. The spell description specifies the specific spell or incantation, save DC, and so on.
Mirrorcast: The spell has the opposite effect of that intended.
Reversal: The spell targets the caster, rather than the intended target of the incantation.