remove_board_game_variables_effect

remove_board_game_variables_effect = {
	# Player-side variables.
	remove_variable = bg_current_round
	remove_variable = bg_current_score
	remove_variable = bg_move_result
	# If there are any wagering counties, clear the blockers on their being wagered.
	if = {
		limit = { exists = scope:bg_stake_land_recipient }
		scope:bg_stake_land_recipient = { remove_variable = wagered_county }
	}
	if = {
		limit = { exists = scope:bg_stake_land_actor }
		scope:bg_stake_land_actor = { remove_variable = wagered_county }
	}
	# Remove any debug variables.
	remove_variable = bg_gib_only_losing_locs
	remove_variable = bg_gib_only_winning_locs
	# Note, we don't remove var:engaged_in_board_game here, as we run this effect at the start of games for clean-up also.
}

As written in game/common/scripted_effects/00_board_game_effects.txt.