I'm the same way. but writing out the entire story that I'm currently thinking out in my head would create quite the wall of text, but I'll take a shot at a more cliffnotes version... super lich guy takes over a world in an alternate reality, then tares a hole in the universe that leads to earth and sends through an army to take over this world as well, while the inhabitants from the first world create a resistance to fight the lich while his forces are spread thin, and at the same time people from our world start gaining the ability to wield magics and use them to fight off these strange new foes, but the hole in the universe tries to heal itself shut, cutting our people off from their magic, and they fear that if they loose magic they will be swiftly defeated by the lich's army that crossed through the portal. so a group of the greatest wizards come together to combine their powers to cast a spell of immortality on one another, in hopes of preserving magic in this world forever, which ends up re-taring the portal between the worlds allowing more of the lich's army through, but two of the wizards find a way to kill the other immortals and plan to become the only magic users left and take over the world, but one of the two has a change of heart and kills the evil wizard before he could kill all the other immortal wizards and opens a portal to the other world from our side and sends in a select group of warriors with magical gear created by the immortal wizards to try and close the riff from the other side, once on the other side the warriors find themselves horribly out numbered and retreat into a strange world of unknown dangers. they are found by the rebellion and help them fight their way through to the top generals of the lich's armies to gain pieces of a magical key to where the lich is resting in order to attack him while he's off guard, removing the original anchor to the tare in the universe, closing it for good and saving both worlds.
