Posted to the EM news site;
All citizens knowledgeable in the ways of explosives and alchemy are needed. In a recent Guard raid in Ilshenar, a particularly dense stone was found blocking the pathway to a cave. The Royal Guard has officially requested the aid of the Mage Tower, and Nimrad the alchemist, in devising an explosive capable of destroying the barricade. Unfortunately their concoction used at Serpent Isle, a directional charge, is not suitable.Submit your explosion recipes, along with the ingredients and a book explaining your device, to the Trammel Mage Tower mailbox. Nimrad will be evaluating and testing these recipes, to determine which is the most powerful.Spellcasters and alchemists completing this task, who are NOT already full members of the Royal Guard, will be considered for future membership in the Mage Tower organization (In other words, use a character that isn’t a Private or higher in the Guard).
You may find the Mage Tower just north of Encyclopedia Magika outside of Moonglow at 72° 15′ N, 133° 2′ W. An occasional moongate may also open to the Tower from Castle Britannia.
Update to clarify the objective: Be creative! Use any existing in-game items, devices, ingredients, and whatever knowledge of chemistry and explosives (real world or UO) that you can. A simple example may be something like… a sulfurous ash explosive with a liquor-based accelerant packed into a keg with a power crystal as the detonator. Except your submission should be a bit more detailed. Put all items used in your explosive into a bag, along with a book explaining the design (and your character name) and submit it to the Mage Tower mailbox.
The EM site itself is here