Hell's Core

Like the name indicates, this spell is as destructive as hell itself. By tapping the most inner forces of the universe, sorcerers can unleash frightful fire explosions that surpass all other spells in their devastating effect and their range of effect. The raw destructive power of the Hell's Core spell is such that it can instantly kill all but the most powerful of creatures that are caught within its enormous blast radius. For this reason it must be used with extreme caution. More than one well-meaning sorcerer accidentally fried his own party members. Worse, the enormous physical and mental strain will leave the sorcerer crippled and drained of mana. A badly placed Hell's Core spell could well be the last thing a sorcerer does before being torn apart in combat.
As the magic potential of a sorcerer is only strong enough to master one such powerful spell, Rage of the Skies and Hell's Core share the same cooldown, before either of them can be cast again.