"Dragons are celebrated in the lore and legends of this world and many others. They are revered. They are worshipped. They are feared. What rubbish! Dragons get hungry. Dragons get greedy. Dragons die. What you really want is the dragon’s fire. Who cares about the lizard? A good sorcerer can summon Dragonfire with no snake at all and use it to smite several foes, one after the other." – The Manual, The Book of Pyro
Dragonfire is a spell that summons a dragon of fire that flies towards, and causes damage to, 5 random enemies.
Dragonfire is useful in chasing down and finishing enemy opponents, as the dragon will fly towards them at a range.
Using Dragonfire for pure damage is not recommended, as you cannot focus a certain enemy, and you cannot move while casting, making you vulnerable while doing so.
It is effective to use Dragonfire before a combat situation happens, as the dragonfire will travel towards the enemy and be an unavoidable threat, which will supplement the damage done by your wizard and units,
Dragonfire is useful in dealing with massed level 1 flying units, as the damage from one attack from the Dragonfire will usually kill them outright.
If the enemy wizard has many Manahoars, it may be more beneficial to save the mana for summoning a creature or another spell.