About Apocalypse Rising 2:
Marrauders are interesting new option which can slow down empires that expand too quickly in the early game – they announce a “raid” and send a fleet which is, at that time of the game, going to wreck your fleets unless you prepare for them in some choke point and support your fleet with a power of upgraded Starbase – even then expect losses.As a bonus there can be a new “mid-game” crisis where a leader (Khan) rises between the Maurauder clans, unites them and starts conquering the galaxy. The thing is that (unlike the end-game crisis) you don’t need to fight them, you can become a “vasal” of the Khan and just wait (with minor economy malus) until he dies, then continue as if nothing ever happened. Collosus is a ship that lets you destroy an entire planet. Actually, based on your ethos you get different options of what the Colosus can do, so e.g. Pacifists can “cover entire planet in impenetrable shield”, or Spiritualists can use so called “God Ray” to instantly turn all pops on a planet to spiritualists, other ethos-bound option is to kill all pops but keep buildings intact etc. However the usefulness of most of these options is quite low because completely destroying a planet might leave behind a mineral deposit but it is always more beneficial to conquer the planet because you get more resources that way.All in all, if you like to role-play Stellaris, then you might like the expansion (e.g. as a Fanatic Purifier you will like the planet.