Constant fog and illusion magic both armies maintain, making the battlefield nearly unobservable.
Both sides at the Southern Front keep a constant litany of fog spells, obfuscation spells, and illusions running. Counterspells and counter-counterspells make No-Man's Land sometimes roil like the sea, and by the time Carl arrives the defenders cannot see anything at all through the rolling fog — only Tran, already in the trench, can report what the cratered ground looks like.
The fog cuts both ways: enemy snipers still pick off soldiers who leave the trench despite the heavy cover, Elle loses track of over a hundred invisible The Madness mercenaries in the smoke, and when the pet bombs appear soldiers along the line first assume they are another illusion. An elf veteran mage has to burn away a patch of smoke to reveal the horde, magnifying Dumplin' like a boss battle notification.
Rolling banks of fog and black smoke that roil and churn like the sea under competing counterspells.
The magical fog of war defining the trench battle, blinding both sides equally.