Sam launching his attack onto Sirius by landing in its moon, freeing the captives, cleaning up the lunar bases from Mental's baddies and moping the floor with Hugo's face.
The Rousing Speech at the end of the Command Center level is a Double Subversion: first the Gnaar ruins Sam's speech on purpose, making it seem like invafing Sirius is a waste of time. But it took a small baby clapping for the rest to join in the assault.
After Sam manages to open a portal in Sirius's shields, we see Sam's ship backed up by thousands of ships manned by Simbas, Zixies, ChiChies and Elvians.
Sam surviving the three Deadly Games and Sirius being invaded at long last!
The entirety of the "Mental Institution" level, as usual per Serious Sam final levels. It's split in several parts, even. Each part consists on waves of difficulty-rising enemy waves which include T-Wrecks, Kamikazes, Soldiers, Kleer, Barbarians, Spiders and Rhino Cybertoys. At some points you get a hovering vehicle whose lasers allow you to tear apart waves without problems. Then you get into a pure Rhino Cybertoy zone. Then into a pure T-Wrecks zone with different turrets. And then into a Giant Spider zone. And if that isn't enough, you'll then get to fight the Final Boss: the Mental Institution itself! Which will spawn countless of helicopters and kamikaze planes towards you and will corner and kill you unless you destroy its core.
