Wildfire
Wildfire is a green substance that is created by the alchemists guild in kings landing, and it is known as an extremely volatile chemical. Once wildfire takes effect it will burn until it is no more, and it can even burn while it is floating on water, making it difficult to handle as well as dangerous. Combine that with the fact that some forms of Wildfire can randomly go off and burst into flames with being simply placed in daylight or moved around too much. No one besides the alchemists knows how Wildfire is made, thought the alchemists guild do claim that it involves magic and is difficult to make. Most wildfire is stored in pots, and these pots can be thrown to create an extremely volatile explosion.
Wildfire can be used to kill white walkers due to it being a fire type weapon, making it a very valuable weapon.
Wildfire is a throwing weapon in AWoIaF. It is great in sieges due to its ability to be thrown easily over the battlements.
It has an area of effect which delivers large damage to surrounding enemies. The AoE does not have friendly fire.
Acquisition
Wildfire can be acquired once you are the owner of King's Landing by visiting the alchemist. Purchasing is limited to a quantity of 9 for 9,000 stags at a time and requires 1 week to create them.