I just realized I don't think I've ever seen an official ruling on this question, even though we've been playing it as close we can to RAI.

So, let's say you've got a big ol' 4x3 Reanimate block with Lingering Dead. It takes 16 damage, wiping out the entire back rank. But the trays are still there, of course, since that's what Lingering Dead does.

Later that turn, Ankaur Maro takes a skill action to add 2 full trays to the back of this unit. These are added behind the empty trays, if you're going strictly by RAW.

What happens at the end of the turn? Is the unit split apart?

We've been playing it where first you add 2 empty trays, then you add 2 trays worth of reanimates, starting from the frontmost part of the unit that has empty slots. But there is absolutely nothing in the rules or FAQ (as far as I know) to support this solution.

This is how we play it locally as well. Though this specific scenario is not clarified in the rules, I do believe that it is intended to work like 38.7 of the Rules Reference:

38.7 When a figure upgrade is destroyed, either through damage or other game effects, its upgrade card is discarded, and its figure is removed from its tray. Then, the figure upgrade’s empty slot in the front rank is replaced with another figure from that unit that could be assigned damage following normal rules.

While this scenario involves no figure upgrades, I believe the intent of the rule is to fill forward empty slots in the front trays from the back ranks. The trays added by Maro are the back most rank now and those figures fill forward until there are no trays in a more forward rank to fill.

Still an official ruling is probably needed, but I believe this pretty much how it is intended to work.

The trays maro adds go behind the empty trays, end of turn the empty trays are removed and the full trays slide forward. This can make the unit have some interesting shapes halfway thru the game.

One time I had a 4 wide with 3 deep on one side, 1 deep in the other, big old L unit.

1 hour ago, Jukey said:

The trays maro adds go behind the empty trays, end of turn the empty trays are removed and the full trays slide forward. This can make the unit have some interesting shapes halfway thru the game.

One time I had a 4 wide with 3 deep on one side, 1 deep in the other, big old L unit.

This implies that units should only fill forward during the end phase. There is no precedent in the rules for that. The only place in the rules where figures fill forward is 38.7, for figure upgrades. In that section the figures fill forward immediately. Lingering dead would then leave the new empty trays to be removed at the end of the end phase, after regeneration occurs.

Not sure how you could have a unit that was 4 wide and 3 deep on one side and 1 deep on the other. The rules for adding trays states: "When adding a tray to a unit, the tray must be connected so it is in the unit's back rank." This means that when adding trays you would fill the back most rank before adding another new rank, which would fill in the middle trays of your back rank. Even if you left the units in the new trays until the end of the turn, it should fill forward before removing empty trays still around because of lingering dead.

Maybe I'm missing something... Do you have a picture of how they ended up?

No picture but it's simple. Had a 4x3 with lingering dead, got hit twice, clearing the back rank and 3 of the second rank, all trays stay until end phase. Maro added 2 trays, and since the unit was still technically 4x3, added them to the back side with 1 tray left on the right.

When I rectified lingering dead, the empty trays removed, and the remaining added trays slid forward, making a 4 wide with 3 ranks on the right, and 1 tray on the left and center left, two trays on the center right.

9 minutes ago, Jukey said:

No picture but it's simple. Had a 4x3 with lingering dead, got hit twice, clearing the back rank and 3 of the second rank, all trays stay until end phase. Maro added 2 trays, and since the unit was still technically  4x3, added the  m to the back side with 1 tray left on the right.

When I rectified lingering dead, the empty trays removed, and the remaining added trays slid forward, making a 4 wide with 3 ranks on the right, and 1 tray on the left and center left, two trays on the center right.

OK, so that's what I understood.... I don't think this is legal. I believe the trays fill forward in the same way that trays are added (that is to say you must fill the back most rank before adding new ones). So the reanimates in the 3 deep side should have filled forward making a full 4 ranks in the front and three trays in the second rank right behind the first. Whether or not this happens before the end phase or not is up for debate, but I believe, based on the apparent intent of 38.7, that the filling forward happens immediately and the trays hang around until the end due to lingering dead.

You might be right, I haven't run reanihammers in awhile so it's possible I was running it wrong.

Glad I brought this up, seems like there are differing opinions of how it works after all.

Regeneration happens at the end of activation of the reanimates too, not the end phase. I’ve played this scenario and have the trays fill the back most rank before adding new ranks. So it will not get an L shape other than 1 rank deep.

3 hours ago, Aetheriac said:

Regeneration happens at the end of activation of the reanimates too, not the end phase.

This is not actually true. Regeneration occurs at the end of the "Activation Phase", not the end of the unit's activation:

Per the rules reference section 6:

6 - Activation Phase

During the Activation Phase, players activate each of their units, starting with the unit that has the lowest initiative and continuing in order of ascending initiative.

6.1 Players resolve the Activation Phase by counting out loud, starting with “one.” At each number during the count, the first player declares if he has a unit with an initiative value that matches that number. If he does, he activates one unit that has that initiative value. Then, the second player declares if he has a unit with that initiative value. If he does, he activates one unit that has that initiative value. This process continues back and forth until both players have activated all units with that initiative value. Then, players continue counting out loud, stopping to activate units as appropriate, until all units have activated.

So the activation phase ends after all of both players units have been activated and right before the end phase. This is different from other units whose ability occurs when they activate, such as spined threshers:

Their ability triggers "After your activation". If regenerate was meant to occur after the unit activates it would have similar wording.

And corrected... thank you i’ve Played that incorrectly for a few games now. ?

1 hour ago, Aetheriac said:

And corrected... thank you i’ve Played that incorrectly for a few games now. ?

We were playing it wrong for like two months over here before we realized it as well. I can't tell you how many times we've had to adjust misinterpreted rules... And we've been playing since the launch...

It's about every month church and I realize we've had a rule wrong in some way or another. Theres a lot packed into the game, lots of nuanced mechanics where wording is very important, and missing 1 bulletpoint in the rrg can have massive consequences.

I think it helps to think of this situation in terms of the figures, not the trays. So at the end of activation, you Regenerate figures, and then in the End Phase, you move any figures from the back rank (that were added by Ankaur Maro) to empty slots in the ranks closest to the front. Again, nothing in the rules states this clearly, but 38.7 as quoted by Quickwhit seems to set this precedent.