While most types of Marine armies get access to the Typhon Siege Tank as a Lord of War option, IMHO the Chaos factions are the ones that benefit from it the most. Let’s take a look:
-AV14/14/14, 6 HPs, and the ability to take Armoured Ceramite, making it basically immune to Melta attacks. Add in the recent nerf to assault grenades and about the only real threats to a Typhon are D weapons, S10 shooting, Eldar Lances, Necron Gauss weapons, and massed S8+ close combat attacks.
-While the Typhon lacks any transport capacity, unlike its “brother” Spartan Assault Tank, it is still reasonably mobile, given its tremendous survivability, and it packs an incredible punch, with up to 2 x Lascannons, a Pintle MM, and most importantly, the Dreadhammer Siege Cannon…. the Dreadhammer fires a S10 AP1 Primary Weapon 7″ Blast with Ignore Cover!!! So, basically the only thing that is safe from the Typhon shooting is something with a very strong Invul save, T6+, and/or Eternal Warrior, all of which are relatively rare in the game.
So, specifically, what does the Typhon bring to the forces of Chaos? Well, right out the box it brings amazing firepower, especially since its main weapon can ignore cover and double out T5 enemies. This means Centurions, SM Bikers, Tau Battlesuits, Eldar Jetbikes, Paladins, Necron Infantry, enemy Plague Marines, Kataphron Destroyers, etc etc. all are VERY threatened by the Typhon. Put another way, the Typhon can be a mortal threat to many of the key, “lynch pin” units in an enemy army, which leads to the second advantage: your opponents can rarely, if ever, afford to ignore it because of its tremendous damage potential. This in turn means that they will have to dedicate significant combat power to try and neutralize it, which plays right into its amazing durability, allowing it to “tank” (literally and figuratively 😉 ) for the rest of your Chaos hordes. CSMs of all types, Khorne Daemonkin, and Chaos Daemons all are MUCH more effective at moving, shooting, and getting stuck into combat if your opponent’s Riptides, Wraithknights, Centurions, Heavy Destroyers, Zoanthropes, etc. are desperately (and often unsuccessfully) trying to bring down the mighty Typhon with all their combined firepower. I think the Typhon combines particularly well with a very “choppy” style of Chaos armies, such as massed Flesh Hounds, Mauler Fiends, Juggerlords, Nurgle Bikers, etc.