7 Hazards of an Old Battlefield

1-Sword Field 

A Sword Field is normally easily seen as a thousand swords floating in the air at chest level, as a magical area denial weapon. When anyone gets too close, the swords stab and slash at them, be they soldiers, civilians, or even small children, until a competent mage or witch undoes the spell.Rarely, an invisibility spell is cast on the swords, which is considered to be against the laws of war in most countries.

2-Restless Dead

The Field of 10,000 Skulls is infamous for them, but many battlefields, particularly the relatively recent ones, will often have ghosts or outright Undead that are either unwilling or unable to pass on to the other side, and may be a danger to the living if they are not given what they want. 

Some might just want their bones to be buried to allow them to rest in peace or pass on into the afterlife, whilst others want to have a message delivered to their living family members, but others want revenge or have gone insane through what they have been through. Some ghosts may only be slain or banished with magical weapons and/or clerical magic.

3-Poisoned Stream

The water that flows on a former battlefield may no longer be drinkable. Perhaps it has become choked with rapidly decomposing corpses from both sides, or filled with cordite after shells the size of cars splashed into it and exploded, or it has been deliberately poisoned to deny the use of the water to the enemy. Boiling it first will lessen the danger that it may pose to the insides of PCs, but drinker beware.

4-Nightmares 

Those who fall asleep on an old battlefield can sometimes have nightmares of what went on there, which wrecks their sleep and can make them less likely to look where they are going and more likely to blunder into hidden booby traps and get themselves hurt or even killed outright.

5-Animated wire

If enough people end up dying on barbed wire, there is a chance that it can soak up enough life force to become animated at an animal level. To stay Undead it needs to feed which it does by sneaking up on people and strangling them to death. It can be slain by clerical magic or by being cut into tiny pieces and thrown into fire or water to prevent the pieces from knitting themselves together and reanimating over time.

6-Giant Vultures 

If the battle was recent enough, giant condors and vultures might be found feeding on the corpses, and they might prefer to fight rather then flee if PCs get too close to them, not wanting to give up a source of what to them is a lot of free food.

7-Booby Traps

From punji sticks smeared with excrement to landmines, some of them made of undetectable things like glass, to bombs disguised as children’s toys, or Undead programmed by a necromancer to rise up and attack anyone not in the military uniform of his country, old battlefields will often have booby traps, and some of them have no time limit set on them and may still be deadly even decades after the war that caused them to be set up in the first place has long since come to an end. PC’s beware.