Worldfire

Worldfire was an extremely dangerous magical ability that allowed a spellcaster to drain energy from another world or plane to empower its spellcasting abilities. Using this ability not only drained the life force of a world or plane, it also damaged the Weave.

Background
According to Elminster Aumar, worldfire was a flashy name for this ability because, unlike other magical abilities such as the spellfire, there were no fire or energy emanations of any kind when someone used the worldfire. This was because using worldfire was so dangerous that spellcasters had to firmly control the raw energy summoned from other planes, not only to protect themselves but also to conceal that they were using this ability. However, in some rare instances fire-based spells were empowered if they were used alongside worldfire.

History
In the late 1480s DR, Mystra had forbidden her Chosen and her other followers to deal with worldfire users, as those individuals were capable of use their ability to drain silver fire, and this could severely damage not only the worlds of Abeir and Toril, but also the Weave itself. However, Mystra compelled all magical-gifted beings, such as mortals capable of use magic or dragons, among others, to openly oppose the use of worldfire.

According to Elminster, a few spellcasters from both Abeir and Toril, became interested in worldfire after the Second Sundering, and they were trying to use worldfire to increase their own powers, regardless of the damage caused to either world. Among Faerûnian spellcasters, the most notorious users of worldfire were the wizard Leoanos Roroebryn, the zulkir Talaskos Murthrond, and the Rashemi witch Velvroame.