A Rift to Abaddon

Rifts are appearing out of nowhere in all random places, Bringing disasters and uncured diseases. Left with no choice, The world was united as one country and military to solve this problem and ventured the rifts one by one only to end up in a total massacre by some otherworldly creatures or fantasy liked monsters. Nearly wiping half of the entire planet's population. Then the world lost hope, until they discover the existence of EXP cubes after successfully killing a single monster. This gives them the ability to grow and play as a user-like system based game, giving them the power to destroy or conquer rifts. And a new social system was created. Now what would you do if a rift suddenly appeared under your bed. This is a story about a young man who stumbles upon a mysterious rift under his bed and discovered that it was a rift leading to a dungeon tower called "Abaddon".