Have a water based Fallen Walker come up out of the ocean and actually move around the area releasing Shanks everywhere. Where it dies lies 2 chest. Mars. In amongst the sand city the streets swell with Cabal roaring defiance. Can you take down the Lieutenants? Or In front if the gate to the black garden a giant Minataur Walks out with a Hydra with it and endless Vex. They war with the Cabal that defend the wall. Only by eliminating both the Minatur and the Cabal Lieutenants will troops stop arriving from the Gate or Cabal drop ships. Thing is. The Hydra gives the Minatur an over Sheild. If destroyed another will shortly arrive if there are any Cabal Lieutenants. On the Moon Hive could crawl from the Hellmouth like Ogres. From both Hive entrances swarm hive troops to join the fight to protect shrines around the Hellmouth area. Basically a large scale Warsat that unless each Shrine is crumbled by our Light all the Hive burn away on the Surface in sacrifice. Venus could have a bunch of Hydras appear on the Steps were the Gate Lord was. As each one is Destroyed more Vex units appear so at the very last Hydra there are swarms about.