Going back to 8th Ed

[Rolling Thunder]

Hallo everyone. After a considerable length of time, I'm contemplating returning the Mercenaries to 40K in the form of a 500pt Militarum Tempestus Storm Scion Grenadier list. Now, GW seems to have laid the indicies for 8th out in the most counterintuitive manner possible: possibly in an attempt to have everyone use the child-friendly power system rather than points. Sarcasm aside, I'm struggling to understand how force composition works in this new era.

For matched play: I add up the model cost and weapon cost of everything in the army - basic weapons like hot-shots and chainswords and the like included?

Also, how do Factions work for battle-forged armies? Does everything have to be of precisely the same faction or else it qualifies as Auxillia?

[RedsandRoyals]

It's all based off of key words. Each unit has their key words detailed at the bottom of the entry that has their stats. Any key word that is enclosed in '<>" can be replaced something chosen from a specified list of options, depending on the factions. That's how Marines choose chapters, Guard choose regiments, etc.

First thing to know about combining factions is that you need to have a faction key word in common to be "Battle Forged", which gets you command points. You never want to take a non- battleforged list, there's just no reason. Fortunately, you can use Imperium (or Chaos, or Aeldari, etc) as a key word. Beyond that, every faction should have it's own detachment (Battalion, Vanguard, Patrol, etc). That applies to different regiments as well. If you try and mix and match within one detachment, they will lose their bonuses such as regimental rules. For example, if you wanted to take Catachans, Cadians, and Ad Mech, putting the Cadians and Marines in the same detachment would mean that the Cadians lose their regimental rules and the Admech will lose their forgeworld rules. That is almost never worth it. If you put the Catachans and Cadians in the same detachment, neither would get their special regimental rule, since they have different key words (CADIAN and CATACHAN, respectively).

Now for the Guard, there are exceptions. Units with the Aeronautica Imperialis (aircraft), Militarum Auxilia (Ogryn and Ratlings), Officio Prefectus(Commissars), Scholastica Psykana (Psykers and Astropaths), and Militarum Tempestus (Scions) can be taken within an all-Guard detachment and not deny them the benefits of their regiment, but do not gain any regimental benefits themselves (Scions need their own detachment to get theirs). So for example, you can take a Scion squad in a Battalion of Cadians and the Cadians will still get their own regimental bonuses, but the Scions will not get any bonuses from their regimental rules or the Cadian rules. Taking multiple formations and staying battleforged also gives you more command points, and you want a lot of them.

The last thing to consider is how abilities interlock and what units they affect. Many characters have abilities that buff nearby units, but some can only buff units that share their <Regiment> key word, while others can buff any unit with the <Imperial> key word. Also pay attention to the unit type key words they affect. For instance, Rough Riders never get the effect of Regimental key words, because they are not <Infantry> or <Vehicles>.

To break it down into simple guidelines...

1. Imperium factions can be taken alongside one another, Chaos factions can be taken alongside one another, etc.
2. Confine each faction to it's own detachment to ensure they get their special key word rules.
3. Pay special attention to the key words in powers and abilities for the units you select.
4. Take as many detachments as you reasonably can, particularly Battalions. That will load you up on command points.

[Aeon]

RT, I highly recommend getting Battle Scribe, to keep up to date with GW's constant and aggrivating erratas to point costs, keywords, unit abilities, etc. I find 8th edition to be well balanced, but insufferably complicated

If you use battle scribe on your phone, you can make a Tempest....err, Grenadier list, and it will tell you all the options available to that "regiment"

Best of luck in resurrecting your bada$$ army. They were one of my favorites to read about back in the day