Powder keg

Powder kegs are barrels which are filled with gunpowder. Although technically employed as a means of transport for explosive material, such containers may be lit and left to explode for purposes of weaponization or demolition. They appear in Ultima VI,  VII,  VII Part Two and,  IX.

Description
Common since the days of the Gargish conflict, Britannian powder kegs are capable of dealing massive damage to the environment around them, and often kill any individuals unlucky enough to be in the range of their explosions. While they can be used as weapons, the motion of combat often makes it difficult to pinpoint who will suffer their effects, making it frequently preferable to employ the against stationary objects, such as bolted doors or blocked passages.

During the Avatar's adventures on Serpent Isle, the hero learned that gunpowder was a little known commodity there, having only recently been developed in the city of Monitor, where knowledge of it was limited to Lord Marsten and Spektor. It would be shown, however, that the ancient Ophidians were well-versed in the fabrication of these explosive munitions, as evidenced by the powder kegs which were found throughout their long-abandoned cities.

According to Vetron's Guide to Weapons and Armour, powder kegs have an effectiveness rating of "16." In Ultima VII Part Two, they are listed as having a damage of 40 and a reach of 16. 

Trivia

 * According to Mandrake, cyclopes enjoy the taste of gunpowder, and will use powder kegs in a manner similar to pepper shakers to season their food.
 * In the SNES Port of Ultima VII, powder kegs are necessary to navigate some dungeons, as certain passages will be walled off and require an explosion to open them.
 * Although numerous powder kegs appear in Ultima IX, almost all of them are unusable, except for a select few found in the dungeon Covetous.