Grim Dawn: Definitive Edition

You need to place 3 dynamites in the detonation site in the Flooded Passage.This will unblock an entrance to the secret area: the Sunken Reliquary.

You can find Dynamite in this Places(beside of random drops in Scrap Piles in Mines and the Outlaw camps ):
-Staunton Mine
-Four Hills
-Cronley's Hideout
-Hanneffy Mine
-Tyrant's Hold
-The Conflagration
-The Immolation
-Stonerend Quarry
-Fort Haron
-Fort Ikon Armory