Complex sentence: The Gastropods, as seen in "The Twin Dilemma" are a race of giant slugs who kidnapped two maths geniuses to pilot their planet into a sun, creating an explosion that will scatter their eggs across the universe.
Split into simpler sentences: The Gastropods, as seen in "The Twin Dilemma", are a race of giant slugs. They kidnapped two maths geniuses to pilot their planet into a sun, creating an explosion that would scatter their eggs across the universe.