A note: I apologize for how late I posted this article, I should have posted it about two-three days ago but legitimately haven't had a chance to check my blog out in that time. I'm deeply sorry for the delay!
Capabilities - I feel the key to understanding where and when to apply a unit in any given situation is informed by knowing their full capabilities off by heart; here is a look at what this unit is capable of.
As per a regular Chaplain, Cassius provides himself and any unit he joins with Hatred (Everything) and Fearless per the Zealot special rule, meaning he provides a substantial boost to the effective damage output of any assault unit by maximizing their to-hit rolls. Giving his unit Fearless does have the downside of preventing them from ever voluntarily going to ground or leaving a combat that they cannot win, but it otherwise ensures they will never leave an objective or flee from an important combat at the wrong moment. Additionally, Cassius himself has the Fear special rule and causes any enemies vulnerable to Fear to take said tests on 3D6 rather than the usual 2D6; while most dedicated assault units have an immunity to Fear, this is still pivotal when fighting certain opponents such as Orks or Eldar. Otherwise, he is capable of taking quite a bit of punishment in a melee due to his Toughness 6 and Feel No Pain (5+) on top of the usual 3+ armour save and 4+ invulnerable save which enable him to survive against most foes, though critically this does not really let him act as a wound-tank against ranged attacks for a unit as the majority Toughness rules will nullify his above-average Toughness value.
His damage output is respectable with four Strength 6 AP4 attacks on the charge that re-roll failed to-hit rolls in the first round of combat via a mix of his Crozius Arcanum - a power maul - and his Zealot special rule, but generally speaking he can't take on any legitimate melee-oriented character and expect to win outside of maybe holding up a challenger that possesses Strength 4 or less. Like any Space Marine, Cassius carries an assortment of frag and krak grenades into battle to ensure he strikes at Initiative when charging through terrain and can throw an anti-tank shot at a vehicle, but generally speaking he will not need the krak grenade in a melee given he already has Strength 6 attacks via his Crozius Arcanum. While he does have a Bolt Pistol which enables him to shoot and then charge a target while benefiting from the dual close combat weapon bonus to gain an extra attack, he also bears a relic aptly named the Infernus which is essentially a slightly improved combi-flamer. Packing Master-Crafted and Hellfire Rounds on the boltgun profile of the weapon is a nice little bonus but it bears mentioning that using this particular aspect of the weapon will prevent Cassius and his unit from charging afterwards given that it does have the Rapid Fire type, leading to some potentially serious mistakes if you unintentionally prevent your expensive assault unit from charging. As an Ultramarine, Cassius can benefit from the three different Combat Doctrines at least once per game which all provide mostly negligible boosts to his damage output, though it is worth noting that using either the Tactical or Assault Doctrines to give himself and his unit a second and third round of "re-rolls" in a protracted combat is a nice bonus to have after the Hatred effect wears off. Otherwise, he is an Independent Character with a mostly unmodified Chaplain profile that has a very limited ability in the form of Preferred Enemy (Tyranids) as befits his status as one of the Tyrannic War Veterans.
Where to Place Them - Positioning is a crucial element of any match, something that is especially true in the adaptive gameplay of 7th Edition; this is my recommendation on placement for this unit.
As a slightly improved Chaplain, Ortan Cassius should always be attached to some kind of assault-oriented unit given that the Zealot special rule is catered specifically towards maximizing the damage output and usefulness of melee attackers. It is also no surprise that the majority of his own offensive capabilities are centered around close combat, ensuring that he makes a good choice for any of the following units to have; Honour Guard, Assault Terminators, Centurion Assault Squads, and either Assault Squads or Vanguard Veterans that lack Jump Packs. These are generally all units that could use the assistance of a Chaplain, though I would argue Cassius' presence is more valuable if the unit in question is considered an "elite" assault unit by Space Marine standards, meaning I probably wouldn't bother placing him with regular Assault Squads given that you won't get as much benefit from what is ultimately the basic melee squad of the codex. As far as deployment is concerned, he can work in a Drop Pod Assault by nature of having a combi-flamer that is still deceptively useful for clearing out light to medium infantry on the drop, while placing him in any transport with his attached unit is generally your best given that he naturally wants to operate at close ranges.
Best Uses - It is true that each unit in the game ultimately has one or a handful of tasks they are best suited for in a general sense; these are the most efficient uses of this unit based on their capabilities.
Ortan Cassius is probably best served being attached to an Honour Guard that is formed up as part of a Drop Pod Assault as he gives them a nice anti-infantry weapon specifically for the "drop" and massively improves their effective damage output when they either complete a charge or receive a charge. Honour Guard are the most efficient close combat unit in the codex and accomplish this by outputting a ludicrous amount of attacks with their power weapons, meaning they get the most benefit from Cassius' Hatred aura given that you naturally gain more value out of re-rolls based on the quantity of dice being rolled. He can alternatively be used to replace the mandatory Chaplain in a Battle Company and thus be privy to all the benefits of a Gladius Strike Force, giving you the flexibility to join him to any number of units while still gaining all the many advantages of using the Space Marines' unique detachment. Ultimately he performs his role more aptly the stronger his attached unit is, meaning any of your dedicated assault units are well placed to serve under his guidance. He can soak up challenges by using his exceptional Toughness value and Feel No Pain (5+) to best or simply outlast the majority of mini-characters and lesser combatants, but be sure to keep him away from any proper heavy-hitter like an Ork Warboss bearing a Power Klaw or Necron Overlord equipped with a Warscythe.
Thank you for taking the time to read this latest entry in my Space Marine Tactica series! I'm definitely not the biggest fan of Ortan Cassius in terms of his place in a competitive Space Marine list but I nonetheless hope you found some inspiration from this article or even learned some useful tips that you can apply into your games with the Ultramarines' Master of Sanctity. If you have any feedback for me or an opinion to share on Chaplain Cassius feel free to post a comment below and I will do my best to reply. Thanks again!
Faith is purest when it is unquestioning.
- Mikelus, Chaplain of the Blood Ravens