Terror from the UnderDeep (5E)

The giant clans have allied - and no one knows why. Hill, stone, frost, fire, cloud and storm giants now work together to collect electrum. Their tracks lead to an abandoned city of the UnderDeep. In these lightless caverns, sinister cultists give the giants' offerings to a misshapen kraken lord. Can your adventurers uncover the secrets behind this wicked alliance before it’s too late?