Distinguish landing a blow, critical damage and special lethal effects.
A full lethal sets a player to 1 HP and 1 CP, or a monster or summon to 1 HP. A half-kill only sets player CP to 1; it halves current HP for monsters and summons, not maximum HP. These changes describe the lethal effect, separately from ordinary skill damage. Invulnerable or non-lethalable targets are rejected. The skill magic level must be no more than 6 levels below the target.
Interlude uses one fine-grained random roll with bounded full-lethal and cumulative half-kill thresholds. Chances depend on skill parameters and applicable attribute and trait modifiers. There is no single success percentage for every dagger attack.
The reviewed RaidBoss and GrandBoss implementations mark these targets as non-lethalable. Ordinary combat damage can still defeat them; a lethal effect is not a shortcut to setting their HP to 1.
FatalBlow checks physical skill evasion and blow success before damage. It separately rolls its damage critical and handles applicable counters. A lethal outcome needs a lethal effect on the skill; successfully landing a blow alone does not guarantee it.