Last time I gave an overview of the General's handbook for Age of Sigmar. If you missed it, you can read about that here. I forgot to address the details of how summoning works in the Matched Play section, and I've had a chance to crunch some numbers and play around with a couple of army lists for my Skaven and Undead.
GW has already released a FAQ for their Age of Sigmar books. One bit in the errata for the Handbook addresses something I brought up about the Path to Glory warbands. I was dismayed by the fact that the Flesh-eater Courts allegiance only offered Crypt Ghouls and Crypt Horrors as followers. It turns out the chart has a typo, and is supposed to include Crypt Flayers as two options. (I suspected as much.)
One thing they don't appear to have addressed in the FAQ is whether a Pitched Battle army's general must have the "leader" battlefield role. The basic rules allow the player to select as their general any model in the army, not necessarily one that you would expect to be the general, like a powerful hero or wizard, but players could choose a random goblin or a catapult.
The new Pitched Battle rules require armies (of any size) to include at least one unit with the "leader" battlefield role. Presumably, that's to include a model that will be eligible to select as the general, but the rules don't specify that the selected model needs to be a "leader." The book simply states that the army roster "must say which unit (Errata changes it to read "model") in the army will be the army general."
Listening to some podcasts, they were under the impression (and it seems like common sense) that the general would need to be selected from one of the "leader" units in the army. They were hoping that it would put an end to some Ogre Kingdom players' dastardly trick of selecting one of the models in a large Ogor unit, knowing full well that the entire unit will need to be killed off before they have to remove the Ogor they've designated as their general. Well, apparently that's still a viable tactic. Maybe in the next round of FAQs.
In the Age of Sigmar, models can summon new units to the battlefield. Death Wizards, for example can summon all manner of undead monsters and infantry to join the ranks of their army. Originally, the only limitation on what could be summoned was being able to successfully cast the spell for the unit you wished to deploy. It was an easy way for Death or Chaos players to field a lot of wizards and quickly outnumber their opponents by summoning unit after unit.
In Pitched Battle games, players can no longer freely summon whenever and whatever they want. Now, when building an army list, the player needs to set aside a portion of their army points to be a "reinforcement points." For example, in a 2000 point army, one might build a list that's 1700 points of units to deploy at the start of the battle, and then hold the 300 points in the reserve pool. There's no restriction of how much or how little you can set aside for summoning. (And this is for anything that will bring new units onto the table, not just summoning spells.)
The points set aside for reinforcements aren't assigned to particular units before the game. ie: In my undead army I don't need to specify that those 300 points will be spent on 240 points of skeletons and a 60 point hero. I can decide what I want to spend the reserve points on over the course of the game– maybe one large unit or monster, or a few small units and heroes.
My initial thoughts about summoning was that it was a waste– The player would essentially be shorting himself on a portion of his army from the start, and those models may indeed never arrive if he can't pull off the spells to summon them. But I'm beginning to see the potential strategy behind it– Units that arrive get to essentially "deep strike" where they are needed on the battlefield, and it's very easy to deny one's opponent the ability to stop the spell by hiding the casting wizard behind terrain. The fact that the summoned units don't need to be selected in advance means that the player can deploy the "meat and potatoes" of his army and use the reinforcements to summon units more suited to the task depending on the army and scenario he's facing. (Need more infantry to hold objectives? A monster or knights to take down a powerful enemy unit? Flying units to cover more ground or get around impassible terrain?) That's not too shabby.
Something else the summoning can be used to get around are the allegiance restrictions. For example, In my undead army, I can field Blood Knights as "battleline" units if the entire army has the Soulblight allegience. Soulblight limits my army to Vampire Lords (with Zombie Dragon), Coven Thrones, Blood Knights, Fell Bats, Bat Swarms, and Vargheists. And that's it, no infantry, no Dire Wolves, nothing ethereal... But reinforcements aren't bound by allegiance (other than holding to the Death Grand Alliance), so I could use summoning to bring in skeletons, wolves, or ghouls during the course of the game.
It's very situational however, as some of the undead sub-allegiances don't even include any wizards. For example, a wholly Deathrattle force could field Black Knights as battleline units, but the only characters available in the Deathrattle list are Wight Kings. So I'd be limited to Skeletons, Grave Guard and Black Knights with no option to summon anything else.
It's important to point out that spells and abilities that add models to an existing unit (rather than bring a new unit to the table) don't cost any reserve points. So the undead banners that replenish fallen troops don't need to have any reserve points set aside for them, but units can't be brought above their starting size in this manner.
I put together a few lists and it looks like the scale of points are pretty comparable to what they were in 8th Edition. A 2000 point army in Age of Sigmar is about the same number of models and units as a 2000 point list in 8th Edition army books. (I'm only looking at Skaven and Vampire Counts, mind you.) One thing that's out of whack are Skaven Jezzail teams. They got a huge point increase, which is fine because they are devastating in Age of Sigmar. (30 of them used to be 600 points, now that comes to 1400 points. Yikes!)
Here's a 2000 point list of 8th Edition Vampire Counts, with a Master Necromancer as its general, a fair mix of troops, and four magic items. The army comes to 1995 points:
The same force, converted over to an Age of Sigmar Pitched Battle army, comes to 1900 points. You'll notice that also includes a third stand of Bat Swarms since they are purchased in units of three, and Doom Wolf leaders for both of the wolf units, since unit upgrades are essentially free:
To round out things to 2000 points, I can drop five Black Knights, add 10 Grave Guard, and then pay for the upgrade for the Deathrattle Horde battalion. Having a warscroll battalion allows me to select another Hero to wield an Artifact of power (giving me two in the army), and I get the battalion upgrades for most of my units, allowing them to re-roll saves of 1 if they're in proximity of another Deathrattle battalion unit, and lets them run an additional 4" rather than rolling to see how far they can run. (Honestly, the battalion warscroll is worth it just for the running bonus, so I can avoid having to make a dice roll every time I move a unit!)
Something else I need to keep an eye on is the fact that Varghulfs have the "leader" battlefield roll. That's easy to overlook, considering they've always been considered monsters, and including them might put me over on my allotment of "leader" units. Other than a few little quirks like that, building an army using the General's Handbook looks like it will play out much the same as it used to.
If anything, players have the freedom to include allied models they normally wouldn't have been able to. As long as the units in the army all belong to the same Grand Alliance (Chaos, Order, Death, or Destruction) anything goes. So an Order army could be comprised of Dwarf and Empire units, all the Elves can intermingle. Skaven are part of Chaos now, so I could put together a Pestilens-themed army that included Nurgle units. Death is the odd man out with only the "Vampire Counts" undead and the Tomb Kings.
I'm waiting for the word to come down that since Tomb Kings are listed under "Compendium" profiles and not under the "Death" profiles that they don't formally count toward the Death Grand Alliance and can't be fielded in a "mixed" undead army. Although, the FAQ does specify that the warscroll keywords are all that matter for determining what Grand Alliance a unit falls under, and the Tomb Kings do have the Death keyword. I guess it will only matter to me if I ever play in a tournament again.