War of the Giants
As shown by the presence of undead giants, the type of destruction found within several cities and referenced in many letters and Imperial notices, the Empire of Yom-Indoth was at one point invaded by a large force of Giants. Several of these letters labelled this event as the “War of the Giants”
Not much is currently known about this war, but so far it has been discovered that the city of Londalorn had ultimately fallen to a force of Giants that attacked by the sea.
It is currently unknown if this event happened before, during or directly caused the fall of the Empire of Yom-Indoth and if it has any relation to the Blight or The Undead that now populate the entire island.