Brushfire

Description
If there are any tiles that have on them at the moment of casting, it is refreshed, causing it to last for another 15 ticks' (6 seconds) worth of damage before spreading even more Flame onto its two vertically-adjecent tiles (top and bottom). This spell does not deal any damage by itself.

Strategy and Synergy
This spell can allow for a Flame build to truly take off, since it has the ability to spread Flames everywhere on the enemy's side if used correctly at an opportune time. You can also maximize damage by casting this spell when an existing Flame is about to expire, so that the Flame would last longer overall. This spell is most valuable in combination of spells that spread Flames either indiscriminately or horizontally, such as, and Flames generated from. This means that it wouldn't necessarily synergize well with as it already fills an entire column full of Flames.

is an extremely good upgrade to have with this spell. This causes the second cast of Brushfire to also affect the Flames that are spread due to the first cast, thus effectively increasing the spread range from 1 to 2 tiles above and below the parent tile that had Flame.

This spell, most of the time, is a prerequisite to getting the Watch The World Burn achievement, due to how it easily spread Flames and more importantly, how it does so even with player tiles.