chance_for_knight_appearance_effect

chance_for_knight_appearance_effect = {
	if = {
		limit = {
			NOT = { exists = scope:activity.var:tournament_commenced }
			scope:activity = {
				any_attending_character = {
					count < 240 #Max is 250, we are leaving some open space.
				}
			}
		}
		random = {
			chance = 50
			every_realm_county = {
				if = {
					limit = {
						save_temporary_scope_as = potential_county
						NOT = {
							any_in_list = {
								list = pool_counties
								duchy = scope:potential_county.duchy
							}
						}
					}
					add_to_temporary_list = pool_counties
				}
			}
			every_in_list = {
				list = pool_counties
				save_temporary_scope_as = pool_county
				every_pool_character = {
					province = scope:pool_county.title_province
					limit = {
						prowess >= 12 #make sure this matches the tooltip of the decision and all the 12s below
						guest_knight_candidate_trigger = { HOST = scope:host }
						is_available = yes
						is_in_activity = no
					}
					add_to_temporary_list = potential_knights
				}
			}
			#Randomize a good knight from the realm pool characters
			random_in_list = {
				list = potential_knights
				limit = { is_alive = yes }
				weight = {
					base = 1
					modifier = {
						add = {
							value = prowess
							subtract = 12
							multiply = 5
						}
					}
				}
				save_scope_as = knight
			}
			#If no one was found, make one
			if = {
				limit = {
					NOT = { exists = scope:knight }
				}
				create_character = {
					location = root.capital_province
					template = pool_repopulate_prowess
					prowess = { 12 15 }
					save_scope_as = knight
				}
			}
			#Cultural Traditions
			if = {
				limit = {
					scope:host.culture = { has_cultural_parameter = better_knights_from_decision }
				}
				hidden_effect = {
					scope:knight = {
						blademaster_lifestyle_rank_up_effect = yes
						knight_increase_prowess_chance_effect = yes
						knight_increase_prowess_chance_effect = yes
					}
				}
			}
			#Add knight to court
			scope:host = {
				send_interface_message = {
					type = msg_tournament_knight_arrives
					title = tournament_knight_appeared_title
					left_icon = scope:knight
					scope:knight = {
						hidden_effect = {
							add_to_activity = scope:activity
							set_location = scope:activity.activity_location
							set_passive_contest_aptitude_and_progress_effect = yes
						}
					}
					custom_tooltip = tournament_knight_appeared_tt
				}
			}
		}
	}
}

As written in game/common/scripted_effects/04_dlc_ep2_tournament_effects.txt.