After placing it, fire or celesthium signals will trigger the blast. There will be a large blast 4 seconds later.

This item is usefull for mining out large chunks of rock without using too much durability on your tools. They are sadly uncraftable as of the “Set Sail to The Ocean!” Update, though you can still find them in the quatzalcoatl temple, either in chests or layed around as traps. Boom eggs are attracted to Powder Kegs and will walk up to them with heart symbols above their head, and in this period, they are distracted and won't attack you, though it's not recommended to try this.