I have downloaded a few mods: Animals Plus, Mo Creatures, Lycanites Mobs, Furniture, Wallpaper, and Twilight Forest. I tried to research the mods before downloading, but I must of missed something. When I go to the Nether, I get picked up and thrown around to my death. When I click on the button that shows the inventory, it says possession followed by a timer, like a potion would have. Does anyone know if this is a regular Minecraft obstacle or if this is from one of those mods? If anyone knows, do you also know how to defeat it?
If you have the mod Biomes o' Plenty installed, then you've encountered one of its featured mobs known as Phantoms. If you can't see them then you have to enable particles in Minecraft's graphics settings.