What does the Raid for Captives casus belli cost?

piety; the amount depends on the titles, claims and distance, worked out when you declare.

Casus belli · Faith wars without a head of faith

Raid for Captives

The war is called “Raid for Captives against …”

Raid for Captives is a casus belli in Crusader Kings III (faith wars without a head of faith). If the attacker wins: Characters and county inhabitants of the defender's realm are sacrificed by the attacker. If the defender wins: No sacrifice is made. Declaring it costs piety. The war goal is worth 1% war score. Patch 1.20.0.3, from game/common/casus_belli_types/00_religious_war.txt.

Quick answers (3)

What do you get for winning a Raid for Captives war in CK3?: Characters and county inhabitants of the defender's realm are sacrificed by the attacker (patch 1.20.0.3).
What happens on a white peace?: No sacrifice is made.
What does the Raid for Captives casus belli cost?: piety; the amount depends on the titles, claims and distance, worked out when you declare.

How the war ends

Attacker wins

Characters and county inhabitants of the defender's realm are sacrificed by the attacker.

White peace

No sacrifice is made.

Defender wins

No sacrifice is made.

If the war becomes invalid

The … has ended: neither main participant openly practices human sacrifice.

Who can declare it

The game shows no text of its own for these conditions; the script is below.

Every faith wars without a head of faith war (the group's allowed_for_character) (16 lines of game script)

OR = {
	top_liege = this
	any_liege_or_above = {
		faith = prev.faith
		count = all
	}
}
faith = {
	NOT = {
		has_doctrine_parameter = holy_wars_forbidden
	}
}
herders_and_tributary_constraints = yes
pam_personal_pacifism_offensive_war_ban_trigger = yes
tgp_dynastic_cycle_offensive_wars_ban_trigger = yes
tgp_war_ban_all_ministers_trigger = yes

As written in game/common/casus_belli_groups/00_casus_belli_groups.txt.

Attacker (allowed_for_character) (8 lines of game script)

faith = {
	has_doctrine_parameter = flower_war_cb_active
}
NOT = {
	any_prisoner = {
		has_character_modifier = designated_human_sacrifice_modifier
	}
}

As written in game/common/casus_belli_types/00_religious_war.txt.

Defender (allowed_against_character) (15 lines of game script)

scope:defender = {
	top_liege = this
	trigger_if = {
		limit = {
			scope:attacker = {
				is_ai = no
			}
		}
		scope:attacker = {
			any_neighboring_top_liege_realm_owner = {
				this = scope:defender
			}
		}
	}
}

As written in game/common/casus_belli_types/00_religious_war.txt.

Cost to declare

Costs piety. The amount is worked out when you declare (by the titles targeted, claims, distance and more), so the script is shown as written:

Cost (7 lines of game script)

piety = {
	add = {
		value = 100
		desc = CB_BASE_COST
	}
	multiply = common_cb_piety_cost_multiplier
}

As written in game/common/casus_belli_types/00_religious_war.txt.

Source: game/common/casus_belli_types/00_religious_war.txt and the English localisation, Crusader Kings III 1.20.0.3. “The attacker”, “the defender” stand where the game names the character; “…” marks other words it fills in during play.