Chief Librarian Tigurius
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.
Tigurius is famous for his unparalleled versatility and high value to any type of Space Marine or even Allied force, and this is most evident in the wide range of traits he can potentially bring to the table. He has decent melee capabilities as befits a Space Marine Librarian by wielding a Master-Crafted Force Staff aptly named the "Rod of Tigurius" that also inflicts Soul Blaze on any unfortunate that faces him in combat. Four Strength 6 AP4 attacks on the charge with the potential for Force makes for decent monster and character hunting potential, but generally speaking his mediocre Weapon Skill 5 and Initiative 4 as well as a low base Attacks value ensures he can't best any dedicated melee combatant without significant luck. He has greater durability than an average Librarian but this is somewhat deceiving as three Wounds, Toughness 4, a 3+ armour save and a complete lack of an innate invulnerable save make Tigurius one of the more fragile commanders for a Space Marine force. Otherwise, Tigurius is also armed with the standard Space Marine wargear selections you would expect; a bolt pistol with Ballistic Skill 4 gives him a tiny bit of ranged presence in the Shooting Phase, while the mix of Frag and Krak Grenades allows him to hurl anti-infantry or anti-vehicular shots at the enemy before charging into a combat with no native Initiative penalties for making an assault through terrain. His melee presence does receive a handy boost if you use either the Tactical or Assault Combat Doctrines which all Ultramarines natively have access to, while his status as an Independent Character with the And They Shall Know No Fear special rule allows him to join all manner of units to spread his psychic gifts.
Tigurius is a psyker and maintains his status as the only unique character in the codex that is analogous to a Librarian, though he exceeds what any generic equivalent is capable of by having an envious Psychic Mastery Level 3. He can generate up to four powers from any single discipline found in the rulebook or split up to three powers between multiple disciplines, with the fact that he has access to all six psychic power lists in the rulebook making him just as versatile as a generic Librarian. Tigurius can re-roll any of the dice to determine what individual powers he generates for each game regardless of the discipline(s) used; seeing as he can make three rolls on any single chart while gaining its Primaris via Psychic Focus, this means you can effectively guarantee incredibly strong powers such as Invisibility. He also gets to re-roll failed Psychic tests which means his chances of getting any power off with the bare amount of dice required are incredibly high - he can re-roll any or all of the warp charge dice used in attempting to manifest a psychic power, though unlike Eldar psykers it does not appear to prevent him from re-rolling successful tests to try and avoid a Perils of the Warp result. Additionally, he retains his Psychic Hood to provide limited psychic defence in a short-ranged bubble which pairs up with his high Mastery Level 3 to make Denying powers much easier than it would be otherwise. Outside of being a super-charged Librarian, Tigurius is also one of only two HQ choices in the codex to natively possess the highly useful Storm of Fire Warlord Trait which, paired with his access to all kinds of psychic powers, allows him to freely mold even Tactical Marines into efficient and pitiless death-dealers at range. Tigurius also packs in a form of reserve manipulation that isn't restricted by making him the Warlord or using him in the Primary Detachment; he allows you to re-roll any Reserve Rolls made for units from the same detachment which is highly useful for Drop Pod-based lists. The important distinction between Tigurius and Sicarius - both of whom are capable of reserves manipulation - is that Tigurius allows you to re-roll all Reserve Rolls, whereas Sicarius is limited to only providing a +1 bonus to those same rolls, providing users of Tigurius the option to delay their own Reserves in a situation that demands it. It is also true that a re-roll usually outshines a +1 bonus to a given roll due to the nature of averages in maths.
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.
What unit you deploy Tigurius with will largely come down to what you feel will need the psychic presence most, or even what squad acts as the best "delivery system" for Tigurius to use his powers to their full effect; usually this means a squad that can take a Dedicated Transport or a very durable unit. One of the prime uses of Tigurius in competitive play is to attach him to a large unit of Devastator Centurions with other characters added to taste such as the awesome Grey Knight Kaldor Draigo, allowing him to focus his powers on Telepathy to provide them near invincibility while the Supreme Grand Master himself teleports them to whatever destination is required via his guaranteed Gate of Infinity power. In more "standard" army lists, Tigurius will usually feature as part of a unit designated to be his bodyguard seeing as many of the best powers in the game are Blessings that do not require any kind of proximity to enemy units for them to take their full effect. However, he is also renowned for being a nasty addition to Drop Pod lists because of his potential to buff his fellow Space Marines' ranged attacks while dealing death in equal measure of his own accord.
Whether he is your Warlord or not, I recommend attaching Tigurius to a sizable unit in deployment or having him inside of a good protective transport - be aware that the latter option will greatly restrict his ability to cast psychic powers, meaning you ideally only want to use it as an added layer of early defence and bonus mobility. Tigurius does not distinguish himself as a melee-oriented character and his fragility due to a lack of invulnerable save often make close combat units a poor choice for him to join, though using him as a close-ranged buffer for those types of units may not be a bad idea. Generally speaking though, Tigurius is favoured by most players because he can plug any gap your army has via psychic powers, his Warlord Trait and reserve bonuses, meaning he can be deployed in almost any unit and moved to any position with little regard to proving his worth in a game. You can use him to bait out powerful enemy units then reposition himself and his squad to a different location with the Gate of Infinity power should Sanctic Daemonology be one of your disciplines of choice, while it goes without saying that any unit affected by Invisibility is darn near impossible to handle and allows him a measure of "random" protection that other characters can't enjoy without psychic assistance.
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.
Tigurius is many things to many players but ultimately he is one of the best overall psykers in Warhammer 40,000 due to being able to access seven different psychic disciplines (counting both sides of Daemonology), re-rolling failed psychic tests in much the same vein as an Eldar Farseer and critically having the rare ability to practically ensure he gets the powers you want. This makes him an invaluable addition to any list built around a "death-star" - the Centurion-star and Wolf-star spring to mind - but it also in general means that you have a really high chance of getting the best powers from any discipline to tailor Tigurius to your needs in any given match-up, making him the unparalleled king of adaptability for Space Marines as would befit his place as an Ultramarine. That he can practically guarantee rolling up the Invisibility psychic power makes him an incredibly powerful character for any game scenario and also lends him his place in all manner of lists built around death-stars such as the two examples mentioned prior, but it is the fact that he is an incredible psyker on top of providing a lot of other bonuses to your army that makes him so fantastic. Storm of Fire lets him increase the damage output of any Space Marine unit exponentially while providing re-rolls to all Reserve Rolls gives him a place in any kind of list based around Reserves, notably those involving multiple flyers, Outflanking units, Drop Pod Assaults and so on. As these kinds of lists are very popular with Space Marines it comes as no surprise that Tigurius is so incredibly popular even outside of his sheer value, and his many different uses are evidence of that. Combining Prescience, Perfect Timing and the Storm of Fire ability on a unit of boltgun-armed Tactical Marines - or even an allied Crusader Squad packed with up to twenty boltguns in a single group - wouldn't even classify as the best use of Tigurius but it will nonetheless allow a rapid-firing bolter-armed unit to devastate opposition in a way that wouldn't normally be possible.
I normally don't like including statements like this in my tactical analysis', but in the case of Tigurius this particular edict is very much true; you can put him in almost any role and expect him to do well because he can bring different psychic powers and other abilities to the table to fit in to whatever plan you might have. He is the ultimate gap-closer in a Space Marine list because his versatility and reliability when determining what psychic powers he can use in each game allows you to use him to swing bad match-ups in your favour long before any dice are rolled. Of course though, Tigurius is not without his downfalls and there are a few considerations to keep in mind; despite being incredibly cheap for what he does, you still never want to just throw Tigurius' life away as he still constitutes an incredibly useful and powerful portion of any army list he features in. He absolutely should not be used to lead an assault as he is simply not geared to take on dedicated melee combatants; you can obviously make him a wound-tank with combined powers like Invisibility and Endurance, Iron Arm and Warp Speed (which turns him into a combat monster) and so on, but if your opponent can match you for warp charge dice and deny Tigurius' powers then he will be left critically exposed and that is rarely something you want to risk in my experience. Be prepared for opponents to single him out the best they can with Assassins and challenges in combat or their own nasty anti-psyker defences as pretty much the entire gaming community is aware of what the Ultramarines' Chief Librarian is capable of and plan accordingly; using him more for defensive buffs on other units in a support role can alleviate that type of pressure.
Thank you for reading my latest Tactical Analysis article, I hope you enjoyed it! The new format allows for a much easier review process even if it does mean the total number of articles is increased thereby drawing out the series' length, though I feel it offers the best balance between advice and review that is also congruent with the time available to me at the moment. I am also eager to hear your thoughts on Varro Tigurius and how he has performed in your games. Thanks again!
We commend our souls to the Emperor.
Let the story of our sacrifice burn across history like a shooting star.
For death and for glory - for the Ultramarines!
- Lucian Ventris, Veteran Sergeant of the Ultramarines