"Going on an adventure is sometimes dangerous."
Translation:모험하는 것은 때때로 위험합니다.
것 is used when saying "the act of doing something", in this case "the act" of going on an adventure is sometimes dangerous. this is also the pattern used when saying "i like doing something" such as "저는 수영하는 것을 좋아해요 = i like swimming or i like to swim. Many time the particle can be omitted however it is still a good idea to learn when and how to use them.