Orb of Lava is an Sorcerer spell.
The caster extends his/her arms to conjure a ball of flame which damages an opponent in a range attack. It has a fast casting time of 2 seconds and a cool-down period of 18 seconds, which means that the caster can use the spell every 20 seconds. However, this flashy attack tends to attract opponents toward the Sorcerer, (who has low HP and Defense ability), and put him in danger.
A notable feature of this spell is that it will only target enemies and weave through them, avoiding friendly fire among allies. This is why Rundelhous Code initially used the spell before the party devised a new strategy.