I think he’s talking about Thunderbolt - it’s a white spell that does decent damage, neutralizing the need to worry about spells being blocked by blue or red mage towers. The Extract Essence on Equestor is fun, but hardly reliable because it’s difficult (impossible) to target a specific tower for destruction in order to get a useful spell.
However, the biggest issue with sorcerers (as has been stated previously) lies in their base attack. To compensate for this, they (allegedly) have access to bigger damaging spells (i.e., southern cross, fireball, thunderbolt, etc). But these spells cost a significant amount of rage, such that even rage runes do not adequately compensate.
One thing that helps with this is the persistent familiar (like Kinnarus, Equestor, Apophet, and Altimorak have). These little guys increase rage regeneration considerably, making it possible for the dragons to fire off their rage-expensive spells often enough to be meaningful.
The only other way to make sorcerers not simply terrible is to give them large-area white spells (i.e., Corthanak), which allow them to destroy the majority of the island’s towers with a single cast, and maybe mop up with a single swipe of the normal attack. Now, I don’t have Corthanak (have a good friend who does), but from what I’ve heard he’s decent but not great.
Next season we should see a mythic sorcerer, so it will be interesting to see what PG comes up with for that. I’m going to hold out hope that it has a familiar.