Hell Fallen
The basic mechanics of the Story Mode version of Hell Fallen. Hell Fallen has no Elite version at this time 
Archaeomachinist: He starts with five stacks of Black Iron which he uses Ancient Artifacts to summon a Black Iron Artifact. The Black Iron Artifacts cast Lifestrip, a laser that charges up and targets people. The incubus also casts Fire Support for some red reticle carpet bombing. His normal attacks chain (and quite widely). Nothing can be interrupted, so the Black Iron Artifacts have to be destroyed.
Arch-Myrmidon: He starts out with four Myrmidon attendants in a canyon with as spouts. He’'ll sometimes buff the Myrmidons with Strategize, cast an electric chain attack, Catastrophic Feedback, or cast Remove Restraints which I am not entirely clear what it does; maybe it starts the purple gas flowing out of the vents. Once all the Myrmidons die, Arch-Myrmidon’s damage absorbing shield will drop and he’ll buff himself with Deathcraze. Nothing can be interrupted here.
Engine Tyrant Prime, Engine Tyrant Alpha, Endjinneers Cinnabar, Tantalite, Borax, and Pyroclore: The fight starts with Cinnabar and Tantalite repairing Engine Tyrant Prime on a wall above. Dropping down engages Cinnabar and Tantalite; after a moment, Engine Tyrant Prime joins the fray. The jinns cast interruptible Firmament Barrage and Combat Biomechanic; the barage summons red reticles to chase people around while the other heals the Tyrant.
After doing enough damage to Engine Tyrant Prime and hopefully killing the jinns, the tyrant heads to the other side of the arena and puts its shield up, preventing any damage. Engine Tyrant Alpha will jump down and attack. The two tyrants will switch off being shielded; a provoke skill is useful to grab a tyrant after it lowers its shield, since they aren’t safe to stand next to when their shield is up. Shielded tyrants cast Firmament Barrage, and anyone close to them when they do gets knocked back and is liable to get targeted by a stationary reticle.
After one tyrant dies, the other enrages, increasing its damage, while the Endjinneers Borax and Pyroclore show up to heal the tyrant. Killing the jinns and interrupting their Combat Biomechanic will shorten the fight; the heal is substantial at this point.
The Executrix: This fight starts in an empty field. When you enter, three waves of hellsoldiers and rakshasa will enter. After all three waves are dead, red reticles targeting each player plus many random ones will fill the area. It’s useful to find a spot for everyone to stand in and try to move together so that the targeted reticles all aim at the same place, making them easier to avoid. After three or four bombings, three waves of incubi and rakshasa show up. After killing them, there are three or four more bombings, after which the Executrix joins the fight personally.
Her attacks chain, and she kites, so can be hard to position. Nothing she does can be interrupted. She has an AoE called Scorched Earth and will periodically revive the rakshasa with Re-Animate, forcing players to kill them again, possibly several times.
Iron Catastrophe, Molten Xenolith, The Primitive Melt: Starting out, only Iron Catastrophe is active. After damaging it enough, it will summon Molten Xenolith. Eventually, one of them will summon The Primitive Melt. All three cast uninterruptible Magmatic Quake, an easy to avoid column attack, and Lava Eruption, which spews out a large AoE of burning lava and shields the golem from damage for a while.
The Ascendant: The fight starts with three House-in-Chains Silencers. Killing one makes all three vanish in an explosive poof of green smoke, and is swiftly followed by a deadly sandstorm. Hiding behind pillars on the left or the right side of the area will protect you. After that, the mysterious figure in the storm will summon five more House-in-Chains Silencers to try to kill Wicker. Wicker can give you a minor heal during this phase if you stand near him.
After those five are defeated, the talking thundercloud will empower one of them, transforming it into The Ascendant while Wicker goes to pick a fight with the cloud. The Ascendant casts an uninterruptible Phase, which scrambles hate around and teleports him in front of the person he intends to attack, where he casts an interruptible Killer Focus, a large column attack. It’s a bit tricky afterward to get aggro back on him; provoking sometimes works, but since it’s story mode, it’s not obvious when he scrambles aggro, and getting people to stop attacking him until aggro is re-established, it really doesn’t matter that much. No one is going to die from being attacked in Story mode.
The Ascendant periodically blocks one side of the area with Electric Smoke Grenade; after he casts that, it’s a good idea to get to the other side, because the storm is going to pick up. He’ll alternate sides once he picks one. Sometimes he’ll drop a single Electric Smoke Grenade, or cast Fifth Column, an interruptible cast which summons more House-in-Chains assassins. Interrupting it just delays the inevitable; he’ll keep trying to cast it until he succeeds.