Now that the chaos space marine codex is a few weeks old, I wanted to put some thoughts out there on a controversial aspect of it, namely the ability to build legion/cult specific armies from the book. This is not a new issue and has been widely debated since the 3.5 codex was around all those years ago. I for one have a few issues with the book, which mainly revolve around the cult issues. Like it or not, it’s here to stay for at least an edition so no point whining about it. Instead I thought I would offer up an article discussing how cult armies can fit with the codex list in order to be represented in a fluffy manner. I won’t discuss the ins and outs of point values, balance etc, so I guess in a nutshell this article is trying to find a nice middle ground as to how the options and fluff can balance out.
Thousand sons are represented in a great way IMO as with the previous edition. They have fearless and VOTLW as do other cult units representing their long-emnity with the Imperium. Specifically, TS have slow and purposeful representing the effect the rubric had on their autonomy. Inferno bolts aura of dark glory and the mark of Tzeentch (MoT) make their favour from their chosen God apparent on the battlefield. Taking a sorcerer with the MoT as an HQ also makes them troops, so you can easily field an army mainly comprising TS without necessarily needing other units.
Before I go further it's worth just mentioning a few rules and fluff points that make Thousand Sons different from their cult equivalents. Firstly, the unit is called by the name of the legion (khorne beserkers aren't called world eaters in their entry for example) which highlights just how unique their formation is. This is further evidenced in the options as they unlike other cult units have VOTLW as standard. This supports that they are all rubric marines whereas say khorne beserkers may comprise both world eaters and other chapters/legions. Furthermore, TSs have several unique items of equipment which are not readily available to other units, such as an aura of dark glory and inferno bolts. A unit such as noise marines may have unique weapons, but in terms of marks and icons it is easy enough to make a similar unit out of regular CSM unlike with TS.
I won’t discuss vehicles as they can’t be marked, but several units spring to mind as being good fluffy units to add into a TS army to complement the obvious TS and HQ sorcerers.(and Ahriman of course) Terminators are the first that spring to mind. If led by a TA sorcerer and loaded out with VOTLW, icon of vengeance and MoT, the only thing that really sets them apart from TS is the lack of inferno bolts. This is a big difference TBH as the inferno bolts remain one of the major advantages that TS have. However, if the terminators are loaded up with combi-weapons then it shouldn’t be too noticeable. Although they can’t be made fearless, mutilators and obliterators can be similarly tailored and thus also fit quite well with the TS theme.
So far one of the most common elements in all the units mentioned is the ability to upgrade to a 4+ invulnerable save. With the exception of HQs, no other units in the codex can do this and so the resilience of other units to low AP weaponry is not as good as the units already mentioned. Therefore it is debatable as to how well they would fit given the above criteria. If you want an army bristling with sorcerers and a relentless horde of rubricae, then something along the lines of the following may work. Again, it probably won’t hold up that well on the tabletop but you get the idea.