Base information

• Minecraft version: 1.12.2
• Mod version: 2.4.5
• Minecraft Forge version: lastast

when i killed chaos dragon i broked the crystal in center, after this happen a explosion, and after the explosion the world started to lag, not in FPS but in tick rate, like 15 seconds to pick a item on floor, i dont know what to do

If will lag until the explosion completed which depending on your PC specs should take anywhere from a few seconds to a couple minutes. If your pc can not handle it then set "disableChaosIslandExplosion" to true in the DE config.