Warpstone Flux Rating: ⭐️⭐️⭐️⭐️
4/5 stars. The rules are good, and very unique within the entire game which makes them a great choice for what they are able to do.
Devoted to their legion and sworn to protect their leaders even unto taking the death blow for their praetors. The companions are the longest serving veterans of the Deathwing and come with a variety of unique upgrades.
The Death Sworn Companions rule is mighty indeed and allows the player to ignore precise shots and strikes, along with the sniper rule, as well as letter the controlling player allocate wounds. This rule alone makes the unit worth taking.
The Deathwing retinue rule means they only are allowed in play alongside a master of the legion and cannot be taken on their own. This is fine.
It is worth talking about their unique upgrade here as well: the Cytheron Pattern Aegis -- at the expense of dropping a bolt gun. The basic way to use them is as a 4+ invulnerable against shooting, or a 5+ against close combat. But when "deployed" at the end of a movement phase by 2 or more members of the squad, then entire squad gets this benefit along with imposing I-1 at the price of not being able to themselves attack. This is mainly worth it, but also worth thinking about how to optimize for this choice.
A truly unique unit of veterans in the entire game. The WS=5 and W=2 combined with artificer armour is just the icing on the cake, let alone the refractor field for the Oathbearer. They can even take jump packs!
5 Companions, all with Terranic Great Swords, 2 Cytheron Pattern Aegis (195 points).
There are lots of ways of configuring this unit. I like the great swords for their sheer audacity. The two aegis are for the initiative drop when required - it won't always be needed and you can keep these guys alive for a while due to being able to allocate wounds. Getting expensive for 5 models though, but worth it still. Take a legion vexilla to taste.