"Its agony leaves our enemies vulnerable. They hear its piteous cries and tremble to think what suffering we have in store for those who stand against us." Man, that just about sums up the theme behind this model. The concept is actually sick enough that one of my most common opponents described the Agonizer as 'horrifying'. When you see the art in the book, it's hard to disagree...
Slow, but decent DEF and ARM for a solo. It also has 8 Damage Boxes, which is great for a solo. His combat stats don't matter, as we'll see. For only 2 points, it's not difficult to fit him into lists, as well.
No attacks. That's not what he's here for.
Fearless: The thing has been through horrors you can't imagine... what's scarier to an Agonizer than potentially staying alive through a fight? Pretty good too, since its CMD is only 6! You wouldn't want it running, after all.
Agonies: First off, they aren't an action. You can run and use them! There are three different ones you can use, and each costs a fury point, and effects enemies within a 4-8 inch range.
- Gnawing Pain: Enemy warbeasts get -2 to damage rolls. I find this the most commonly helpful, since it can really help keep your tough Skorne beasts and your warlock alive. 10" run + 8" agony means that you could also use this to go stop a ranged warbeast somewhat too. Of course, they could just go after the Agonizer, but that does help preserve the rest of your army.
- Maddening: Enemy warbeasts are -2 THR. It's good, but it's not as common to find uses, although late game it would probably come in handy. Dropping someone's THR from 8 to 6 is a MAJOR threat if the beast has 1 fury left on it, 9 to 7 is nice, and 10 to 8 still increases the chances of failing. There's potential for some serious game-shifting potential here, just not always applicable.
- Spiritual Affliction: Enemy warbeasts can't use their animi; warjacks lose the use of their arc node, nor can be allocated focus for a round. This is the only Agony that works against Warmachine. Against Hordes, this could be awesome. There are some great Animi that warlocks depend on- stopping their use for a turn, or forcing a beast to get away just to allow the use of it, could really screw with your opponent's plans. Against Warmachine, as Ian points out in the comments, this can be quite devastating. Some jacks absolutely need focus to be effective. Not getting it can really hamper the effectiveness of the army. This is a great denial ability, and against some opponents will probably cause the Agonizer to draw a lot of fire.
Fury Bank: This is how the Agonizer gets the fury he needs to use his Agonies. Early on, you'll have some spare fury, so it's not hard to fill him up with the 5 max he can have. Later on, if he's still alive, he can fill in for potentially dead beasts to give you that fury back. In some ways, he may be worth taking just for this, but if you're depending on him to get your fury, you're probably pretty screwed anyway. Like I said, it shouldn't be a problem to fill him up by turn 2.
Master Tormentor Morghoul: Inflict Pain + Maddening could be incredibly effective mid/late game to get a warbeast to frenzy at a useful time.
Archdomina Makeda: Not really much... but she becomes even harder to kill in combat when backed up by an Agonizer.
Titan Gladiator: Not much, although Gnawing Pain helps keep it alive once it's in combat.
Cyclops Savage: Not much, although Gnawing Pain helps keep it alive as well.
Titan Cannoneer: Same as the other beasts. Not really much synergy, just an ability to keep the beasts alive once they are engaged.
Paingiver Beast Handlers: Inflict Pain + Maddening is still great here- a full unit can add another 6 fury total to opponent's beasts, and the decreased THR can really screw with the opponent's plans.
He can be taken in Hexeris' theme force, which will virtually ensure he can be stocked up on focus turn one, since the upkeep spells are free.
Void Seer Mordikaar can take an Agonizer in his theme force as well.
Dominar Rasheth, however, actually requires Agonizers. First, for every Titan you take, you can take an extra Agonizer. For tier 3, you're required to take 2 Agonizers (starting them each with 3 fury points). I'll have to actually play with Dominar Rasheth to get a feel for the synergies for them, but they do seem to be great targets for Dark Rituals.
It's only two points- and there's always something it can do for you. Against Hordes, it's more versatile, but it certainly has some pretty effective ways to screw over warjacks as well.
It's a quite disruptive piece that's versatile in its role, and should definitely get under your opponent's skin, especially on crucial turns. Definitely consider taking one.