Nuke

The Nuke is the most powerful explosive spell available in the game, launched as a somewhat slow arcing projectile. It is capable of destroying the most dense Materials in the game, such as the brickwork in Holy Mountains and Extremely Dense Rock.

Usage
While their primary usage is combat, Nukes are highly effective at clearing out large sections of softer terrain, and will soften or considerably destroy harder terrain in large amounts as well.

Nukes have an enormous explosion range, in many cases larger than the size of the screen. If the thing you're aiming at is visible on-screen, you are probably too close. Explosion Immunity is highly recommended if you plan to use them with any regularity, and the Speed Up spell modifier is recommended to avoid the projectile falling too far due to gravity and landing too close by.

After the explosion, chunks of material will break loose from the ceiling and rain down as solid chunks of fallen concrete similar to the Earthquake spell. These chunks do large amounts of damage to anyone caught beneath them, but are always soft and easily dug out afterwards as the original material of the terrain is replaced by a softer concrete material.

Giga Nuke
A stronger version of the Nuke, almost twice the explosion radius and damage. The blast sends out a wave of radiation, transmuting liquids and powders into toxic sludge, and solids into toxic rock. Obtaining the spell requires following a different quest.

Tips

 * Even if you are immune to the explosion itself, you'll still be set on Fire unless you're immune to that too. Keep water handy.
 * Do not let wands with this spell lie around in the world where you suspect enemies might travel. They'll pick it up and fire it without hesitation with no regard to their own safety, or yours.
 * The explosive force of the Nuke is stronger nearer the center. Harder materials, like Glowing Stone, may survive further out and can be used for cover.