To bring up one that probably isn’t the most popular here but is on other sites, I’ll bring up a species that is quite a bit off the beaten track:
The Gems, from Steven Universe!
Now, the main source of conflict would be the way Gems reproduce-that is to say, draining the life from the planet until it’s reduced to a hollowed shell of its self, as demonstrated below is what they planned on turning Earth into:
While Gems are exactly what they sound like, they are able to generate a physical form from light, usually taking on a human-like form (although they can shapeshift, naturally.) These forms can be disrupted (especially with electric or piercing weapons), but doing so doesn’t kill the Gem itself; rather, shattering the stone would do so, with even cracks causing deformations in their personalities. That said, they don’t age or need to eat, drink, breathe, or sleep unlike organic life forms, as well as are substantially faster and stronger than humans, so they can still be plenty dangerous, even when not regarding the fact some possess supernatural powers (although they don’t always use them for combat.)
Even when shattered, the pieces live on, although they’re barely sentient at that point and are a mere fragment of the original being. This is, understandably, is a pretty bad deal, with death being much more preferable.
Interestingly, if a Gem shapeshifts a womb for themselves, they can become pregnant, although the child will be the species of whatever they are mating with (although they can sacrifice themselves in order to produce a hybrid being.) By implication, one can assume a gem can manifest male genitalia and produce sperm.