There is no definitive answer to which house rules unforeseen events in a mundane chart, as different astrologers may have different opinions on this matter. However, some possible candidates are:
The 8th house, which rules death, transformation, crisis, and the occult. This house may indicate events that are sudden, shocking, or life-changing, such as natural disasters, wars, accidents, or assassinations1.
The 11th house, which rules groups, friends, hopes, and revolutions. This house may indicate events that are related to social movements, collective ideals, or rebellions, such as protests, riots, coups, or reforms23.
The 12th house, which rules endings, secrets, karma, and the subconscious. This house may indicate events that are hidden, mysterious, or spiritual, such as scandals, conspiracies, revelations, or miracles23.
Of course, these are not the only houses that can show unforeseen events in a mundane chart.