"I refuse to fight an enemy who has the ground itself at their command! War is about gaining strategic ground, but what do you do when the enemy changes the rules of Nature?"Quicksand is a second-level nature magic spell in Heroes of Might and Magic IV that costs three spell points and creates a patch of quicksand, the size of which is based on the caster's level. All targets require a full turn to move through 2 feet of quicksand.
A unique spell, Quicksand can perhaps be the most powerful spell in Nature's arsenal - in the right situation. If your army has decent ranged damage capacity (from an Archer hero, elves, faerie dragons, water elementals etc.) you can devastate non-flying (or bound-flying) creatures with a few casts of this spell. Its use can be somewhat tricky, though the visible laying path introduced in the 3.0 patch helps greatly.
Quicksand works best when you can use the combat terrain to create bottlenecks. Leaving a narrow path open and blocking off the wider paths with long branches of quicksand will encourage the enemy creatures towards the narrow path which you can subsequently block with masses of quicksand. Now, no matter where the creature moves along your quicksand wall, you can apply more to prevent it breaking through and you can attack from range with impunity until you run out of arrows/spell points. This tactic is especially applicable to bridge, castle (defending) and ship battles where there are natural bottlenecks.
Water elementals can also cast Quicksand. If you have these creatures in your army, consider splitting one or two individual Elementals into their own stack to cast Quicksand while the primary stack casts Ice Bolt.