Courtesy of GaleRazorwind:
The Hive Tyrant is a very powerful, but expensive, HQ unit. It can take many different loadouts to fulfill various roles in the army. It has psychic powers, special abilities, powerful weapons, and heavy combat potential. It is also a vital provider of Synapse to keep the lesser creatures in line.
1. Great weapons
2. Monstrous Creature
3. Amazing support abilities
4. Synapse/Shadow in the Warp
1. Gets expensive really fast
2. Big/high priority target that is difficult or expensive to hide
3. Only has a 3+ save and no invulnerable save
Lash Whip and Bonesword: This comes standard. The Lash will give the Tyrant an edge in CC thanks to the reduced initiative. While his I is usually sufficient to go first, the lack of assault grenades means that a charge through cover would result in going last, but the Lash will allow you to go simul with those in base contact. The Bonesword is a bit of a waste as MCs already ignore armor saves. The only plus is the ID potential.
Scything Talons: Also comes standard. These things can be very useful to almost any build. With the Tyrant's WS, he is likely hitting on a 3+, so being able to reroll half of your misses is a very good thing, especially considering his relatively low number of attacks.
More Scything Talons: Having 2 pairs of Talons may be a bit of an overkill. Even a Tyrant that specializes in CC may be better off taking a gun. As mentioned above, with a single pair, you are already hitting on 3+ and rerolling half your misses, so the free set of Talons have an opportunity cost of spending points for something better.
Twin-Linked Deathspitter: This is a cheap option for giving a Tyrant a ranged gun, but a TL Tau Burst Cannon isn't exactly a very fearsome weapon. The twin-link doesn't make up for the low number of shots.
Twin-Linked Devourer with Brainleech Worms: The "Dakka-Tyrant" is alive and blasting! The Devourer has a few changes. First, there is no longer a reroll to wound, however, with S6, you are generally wounding on a 2+, so it doesn't make a whole lot of difference. Two pairs of these on a Flyrant with Old Adversary is a very deadly mix of speed and power. There are plenty of times when you are out of range or will gain little benefit from casting Paroxysm, so the added firepower is very nice to have available. Old Adversary will allow you to retain your rerolls to hit (as well as give this ability to nearby units).
Stranglethorn Cannon: This seems like it would be a good choice for some anti-infantry firepower. A good strength and Pinning are nice for taking out infantry and supporting your little guys on the advance, but it becomes fairly useless once you reach enemy lines as there is too great a risk of shooting your own guys.
Heavy Venom Cannon: This is a very popular choice for Tyrants as it gives a good platform for shooting vehicles. Whether you even do anything to those vehicles is a very different story. I've seen them used in multiple games and do hardly anything, mostly because they fail to even glance, but that could be chalked up to poor rolling. If you glanced, you have to deal with a -3 modifier to the damage table, but if you pen, you don't have to worry about the vehicle blowing up.
Thorax Swarm: This is a fairly expensive option that will not likely be used more than once, as Tyrants tend to die quickly. Add on the fact that you can't take it with wings, and suddenly the ability to fire a flamer on top of your other weapons becomes a bit moot since you may never get into flamer range in the first place.
Hive Commander: This is one of the more popular choices. The boost to reserve rolls is incredibly useful for supporting a reserves army, and you even get to make a troops unit outflank, too. I suggest outflanking a unit of Hormagaunts as they can likely reach a viable target from the board edge, but they aren't too expensive and won't be missed if they get plastered.
Indescribable Horror: This is probably the least taken choice. It basically gives you "The Horror" power from the old codex, except you have to pay a chunk of points for it and it can't be as effective as it was, and the main reason for that is that you can't run a Psychic Choir list anymore, so there isn't a -5 Ld penalty to put attacking units at Ld3-4 when they make the morale test. Without that modifier, it is a breeze for most units to pass the test, and now your fancy upgrade does nothing.
Old Adversary: This is likely the second most popular choice. When given to a Tyrant with wings, you can quickly move your "bubble" across the field to give Preferred Enemy to nearby units. However, it may be difficult to get your Tyrant where he is needed if he has to walk.
Adrenal Glands: A Tyrant has little need for Furious Charge unless you plan to send him after vehicles. He is already I5, so he goes before most things, and with S6, he already wounds most things on a 2+. Having S7 on the charge will make cracking vehicles much easier, though. Against regular vehicles, you'll be penatrating on a 4+ on 2D6, and against all those AV12 walkers, you'll only need a 6+ on 2D6 to penatrate. AV14 is still a tough nut to crack with an 8+ on 2D6.
Toxin Sacs: This is pretty pointless. A 2+ to wound is better than a rerollable 4+ to wound. This would only help against the things with crazy high toughness (C'Tan/Wraithlords), or against other T6 creatures.
Acid Blood: This is unlikely to do much if your Tyrant never makes it into CC, but a Flyrant may find a use for it. Depending on whether the limit on how many wounds you can cause with this is the creature's current number of wounds or if it is unlimited (waiting for FAQ), you may have only one or two wounds left by the time you reach combat, so it could be very ineffective.
Implant Attack: This is another chance to cause Instant Death, and is probably about as likely to cause ID as the Bonesword the Tyrant starts with. Unless you plan to be going after multiwound enemies, don't bother taking this.
Toxic Miasma: This is a neat defensive biomorph, but, like many of them, it is so highly situational that it is likely going to do nothing. It is rare to have a Tyrant locked in combat for more than a turn, as either the Tyrant dies or he kills the enemy/sweeps them.
Regeneration: This is on the cheaper side for Regenerate, but the odds of having it do anything on a 4 wound model are slim. The Tyrant will either be dead before he uses it, or he won't have enough damage caused to him to increase the probability of rolling a 6. Save this for the 6 wound models when you have points to spare.
Armoured Shell: Yay, we can give our Tyrant a 2+ save for almost twice as much as it used to cost. I think you may be better off spending a few more points on a Tyrant Gaurd so you can get cover saves from little things and siphon off some wounds from the main event.
Wings: As if our wings weren't overpriced in the last dex, they actually made them more expensive! However, this is just about the only biomorph that is actually worth taking, though it would not benefit all builds. As mentioned earlier, a Flyrant is great for CC, as well as bringing Old Adversary to bear.
The Tyrant gets any two of the following four options:
The Horror: Meh. Without any negative Ld modifiers, this power is likely going to do nothing.
Leech Essence: This is a useful power. This is the other way you can regain lost wounds, and likely better than Regenerate ever could. Use it when you're hurt and don't need to use a different psychic power.
Paroxysm: The other useful power. This is best used with a coordinated assault by another unit like Hormagaunts or Termagants. Making your Hormies and Termies hit on a 3+ and having the enemy hit you back on a 5+ is a beautiful thing! It will greatly increase the survivability of your models.
Psychic Scream: Spirit Leech Lite. The whole Ld test + wounds for each point failed is probably going to do nothing but waste time rolling dice. A 2D6 Ld test is very easy to pass, and unlike the Doom of Malan'Tai, the Tyrant does not regain wounds from this attack. Just leave this attack to the proffessional (The Doom).
The Hive Tyrant is a powerful fighter, but he is a bit of a lightweight when it comes to taking fire, so you need to protect him. While he is more than capable of wreaking havok on his own, he is most useful when he is supporting the rest of the army. This is either achieved via abilities like Old Adversary or with the psychic power Paroxysm. In order to keep him alive on the approach, take him with at least one Tyrant Gaurd and create a traditional tiered line of Nid cover (E.G. Termagants in front of Hormagaunts in front of Venomthropes in front of Tyrant and Gaurd).
I believe the two most common builds are based on either Hive Commander or Old Adversary, and usually look a little something like this.
Hive Commander: Heavy Venom Cannon, Scything Talons, Hive Commander, Leech Essence, Paroxysm, 1-3 Tyrant Gaurd.
This build is great for supporting a reserves list. The Tyrant can start on the table and shoot at stuff from long range until your main force arrives, while the bonus to your reserve rolls helps to ensure more things come on as soon as possible. He can then move forward to support incoming units with Paroxysm.
Old Adversary (choppy): Either Lash Whip and Bonesword and Scything Talons or two pairs of Scything Talons, Old Adversary, Wings, Leech Essence, and Paroxysm.
Old Adversary (shooty): Two Twin-Linked Devourers, Old Adversary, Wings, Leech Essence, and Paroxysm.
This build is meant for rapid response and close support of your troops. It is meant for getting Preferred Enemy to the area that needs it most, and providing covering fire/extra CC punch when it gets there. I listed two different weapon loadouts because they have the ability to specialize for a price or to conserve points. The choppy build saves you some points as those weapons are all free/standard, and while Preferred Enemy gives you rerolls against things with WS, it doesn't help at all versus normal vehicles, but the Scything Talons do work. Now, if you aren't bothered by the lack of rerolls against vehicles, and have some extra points, going with the "Dakka" option will maximize the amount of anti-infantry potential the OA Tyrant can bring to the field.
Personal Experience and Opinions:
I rarely use a Tyrant anymore, which is sad since I used to use two of them all the time with the old codex. They have simply become so expensive that they are really a "luxury" unit. If I'm not playing at at least 1850 points, a Hive Tyrant is simply not going to fit into my list. I do love having one, even if it only lives through turn 2, as I love running a reserves heavy army and that bonus makes a huge difference in how many of my guys come in on turn 2. Other than that, he tends not to do much but sit there and look pretty with the radar dish on his head (enhanced senses). And it is for all of these reasons that a 200 point Tervigon is my HQ of choice.
Courtesy of Marikar:
MC = big scare factor
able to join unit of Tyrant guard
can be given 2+ save
can be given wings
New psychic attacks/options
can ID enemies with Bonesword
More attacks standard than it used to have.
basic SM level save.
Cost is going to be 200+ for a usefull tyrant and he will be a fire magnet.
Anti Psyker armies mess his abilities up somewhat. ie Eldar runes of witnessing etc....
Hive Commander - usefull as it aids the bringing on of reserves and allows a troop unit to outflank (outflanking tervigon!)
Indescribable Horror - This is the Horror power he used to have. With the large number of fearless units in the game this is next to useless. But it could be really effective against IG armies.
Old Adversary - My favourite as it gives preferred enemy to all units in 6" The only drawback is the need to keep up with the front lines of your assault to benefit from this and some units that have re rolls to hit already won't benefit at all.
The Horror - a ranged version of Indescribable horror making a unit fall back if it fails a moral check. Again useless against fearless units. There are other powers that are much better.
Leech Essence - A good power to take as it is up to 3 hits at ap2. The Tyrant gains the wounds back for itself.
Paroxism - Also a good power as this reduces the enemy's ability to fight reducing 1 enemy unit to WS and BS of 1
Psychic Scream - Can be usefull against low Ld enemies, but is a bit hit and miss. This power currently needs a FAQ to clarify what it effects.
Bonesword & LashWhip - Power weapon that has the possibility to ID. LW reduces I of enemies in base contact to 1
a usefull combination for a CC Tyrant. The bonesword gets better if you use 2 of them.
Scything talons - Grant re rolls of 1's . Useless if you have taken the Old Adversary rule, otherwise a cheep way of getting re rolls to hit.
Deathspitters - Not a good option for a Tyrant as there are other ranged weapons with better strength for the same cost.
Devourers with Brainleech - much better option than the previous as the Strength is higher.
Stranglethorn cannon - a good strong choice for anti infantry, not very usefull for antiarmour.
Venom Cannon - a good Anti armour choice, but very weak against heavily armoured vehicles like the LR or Monolith and particularly poor against Eldar tanks with protective runes.
Adrenal Glands - Not worth taking on a tyrant since you will generally have a higher I and S7 isn't any better than S6 IMHO.
Toxin Sacs - again not usefull unless you are going up against very high (T9 - 10) enemies, especially since this will actually reduce your chance to wound any creature with T4 or less.
Implant Attack - causes ID but is not really that usefull unless you are going character hunting. not the best use for a Tyrant .
Toxic Miasma - again this is simply not effective enough to be usefull.
Regeneration - High cost for a poor chance to gain a wound back. The Psykic power Leech Essence is much more usefull and does the same. Although this works when you are locked in combat.
Thorax Swarm - A close attack template that I don't think is good enough to justify the cost. I can't see a tyrant getting to use this more than once a game if at all.
Armoured Shell - This is very usefull as it gives a 2+ save.
Wings - Very costly but excellent upgrade for a Tyrant.
There are only really 2 options .
1. Turn your Tyrant into a CC monster and decide if you want to get into the fight very quickly. If so then use wings. The other option for a CC tyrant is to take guard. Give him Armoured shell and walk him up to the enemy, but try to make sure he has cover. Note that a Tyrant in combat with an enemy with power weapons is not very survivable. especially if the enemy has high enough strength and an invulnerable save.
2.A support Tyrant. Give him a good shooting weapon and sit back. The drawback with this is its an expensive gun platform and there are cheaper ways of getting those. (A fex, just!)