Photography

Enchant creature, when enchanted creature is alive, you gain 1 life each turn. If creature dies, you may add a +1/+1 counter to any creature and discard this enchantment.
This increased the emotions of the people who see the battle.
Caused the first forged photographs even with Lincoln.
People took pictures of soldiers.
Photography showed citizens the horrors of war in their entirety for the first time. This shifted public opinion and continues to be used today.