------Introduction------
I started playing on Showdown about two weeks ago, and I've had a lot of fun playing stall in Natdex AG. Initially I wasn't sure if stall could even work in NatAG, since the offensive threats in the tier are, well, in a tier of their own. However, the prevalence of horrifying offensive threats in the meta greatly restricts the number of viable threats, thus making team-building somewhat easier. It is much easier to prepare for specific threats when you can be reasonably confident that you'll face them. As of now, I'm #27 on the ladder even though I'm by no means a fantastic player, so I'm fairly confident that stall can work. I'm writing this because I'd love to hear what more experienced players think about the team. Before proceeding, I would like to note that the team is very much a work in progress---I'm constantly tweaking things to better handle problems I discover while playing.
------The Team------

Arceus-Dark @ Dread Plate
Ability: Multitype
EVs: 248 HP / 252 SpD / 8 Spe
Calm Nature
IVs: 0 Atk
- Judgment
- Toxic
- Recover
- Defog
Arceus-Dark is surprisingly useful in this meta. First of all, lots of legendaries have a Psychic typing, which makes Arceus-Dark quite threatening. In particular, I use Arceus-Dark to counter Calyrex-Shadow. Since Arceus-Dark is immune to Psyshock, it runs max SpD to better handle Calyrex-Shadow's bug and fairy moves, which it tanks quite well. In general, Arceus variants can be worn down by hazards quite easily since they cannot use Heavy-Duty Boots or Leftovers, so it is important to Defog when will force your opponent to choose between losing some momentum or reapplying their hazards. Toxic is a good way to put a lot of special attackers on a timer, but be careful about using it on Calyrex, since it often runs Substitute. Unfortunately, I don't really have room for Refresh on this mon, so it often requires cleric support from Chansey, which can be hard to pull off if your opponent doesn't let Chansey come in.

Arceus-Fairy @ Pixie Plate
Ability: Multitype
EVs: 252 HP / 252 Def / 4 Spe
Bold Nature
IVs: 0 Atk
- Judgment
- Recover
- Refresh
- Will-O-Wisp
Arceus-Fairy is sort of like the core of the team. If my opponent has a Zacian-Crowned, I often lead with Arceus-Fary. If they lead with ZC, I switch in Quagsire (see below), and if they don't I often go for a Will-O-Wisp unless they've lead with Primal Groudon, since people typically like to switch in ZC on Arceus-Fairy immediately. Recover and Refresh let Arceus-Fairy stay in and even PP stall common Toxic users like Ho-Oh and Lugia. While its damage on these foes isn't spectacular, it does effectively stall them out. It can easily punish Mega Rayqauza, but it does struggle to switch in. Arceus-Fairy walls lots of common threats (like, for instance, Marshadow, Urshifu-Dark, Calyrex-Ice, and even most variants of Primal Groudon) and is just a generally useful mon to have. It does well against Yveltal, though it can struggle against its Max Airstreams. Typically, I like to Will-O-Wisp Yveltal if I think it will Dynamax, as Chansey can then tank its physical Max Darknesses quite well and needn't fear losing its item until the Dynamax ends, in which case Arceus-Fairy can come back in.

Lugia @ Heavy-Duty Boots
Ability: Multiscale
EVs: 252 HP / 252 Def / 4 SpD
Bold Nature
IVs: 0 Atk
- Toxic
- Aeroblast
- Ice Beam
- Roost
Lugia is a great mon to switch in on almost anything. Of course, you don't want to switch Lugia in on things that simply counter it, but often, when I'm in doubt, or even when I just want to scout moves, I'll switch in Lugia. I run Heaavy-Duty Boots to preserve Multiscale, and in general, it's a good idea to keep Lugia at 100% HP until the mons its supposed to check (such as Mega Rayquaza) are dealt with. I run Ice Beam to punish unsuspecting Mega Rayquaza who stay in on Lugia. Max Def investment and a Bold Nature allow Lugia to serve as a blanket wall and scout against various potential threats. Toxic is nice in general, although I'm thinking about running Will-o-Wisp instead to cripple physical attackers, as I've found that Toxic lets bulky steel types switch in for free. Aeroblast is there so that Lugia can get a speed bonus if it Dynamaxes. In general, I tend to Dynamax when it benefits me offensively and defensively. For example, a Dynamax'd Lugia can check Mega Ray with ease, while a Dynamax'd Arceus-Dark can shrug off a +2 Draining Kiss from Calyrex-Shadow.

Arceus-Ground @ Earth Plate
Ability: Multitype
EVs: 240 HP / 252 Def / 16 Spe
Bold Nature
IVs: 0 Atk
- Judgment
- Rest
- Sleep Talk
- Roar
This slot has changed more than any other. At the moment, I'm running Arceus-Ground to deal with Primal Groudon. I run Rest and Sleep Talk for a few reasons. First of all, sash Smeargle is a common lead and can give the team lots of problems. Initially, I ran with Mega Mewtwo-Y (for the Insomnia ability) and Taunt. While this effectively dealt with Smeargle, it often struggled to accomplish much against common threats in the tier and it was worn down rather quickly. Sleep Talk Arceus Ground can still threaten Smeargle even after it's put to sleep, and a Judgement will either do lots of damage to it (and perhaps catch them off guard), while a Roar will force the Smeargle out before it can Baton Pass to something more threatening. I typically lead with Arceus-Ground when I see an opposing Smeargle so that I can Judgement immediately. Rest+Sleep Talk can sort of function like Recover+Refresh, and the surprise factor is nice. Ultimately, I chose Arceus-Ground because I wanted something I could confidently switch in on Primal Groudon. The mon does have its drawbacks though---it's super easy for the opponent to switch in basically any flying type. On the bright side, I won't be swept by swords dance Primal Groudon. The 16 Speed EVs are there to outspeed any neutral-natured Primal Groudon.

Chansey (F) @ Eviolite
Ability: Natural Cure
EVs: 252 HP / 4 Def / 252 SpD
Calm Nature
- Toxic
- Aromatherapy
- Soft-Boiled
- Seismic Toss
Chansey's role is simple—she simply walls most special attackers. While most Chansey sets run mixed bulk, my Chansey is entirely dedicated to SpD because the special attackers in AG are sufficiently scary. For example, this Chansey loses 34-40% of its HP from a maxed SpA Primal Kyogre's Water Spout, which means it can safely switch in on it. A mixed-bulk Chansey would not necessarily have this option. Of course, having almost no Def at all requires careful play. In particular, Psyshock and Psystrike will simply obliterate Chansey, but fortunately most mons who run these moves are covered by the rest of the team.

Quagsire @ Leftovers
Ability: Unaware
EVs: 248 HP / 8 Atk / 252 Def
Relaxed Nature
- Earthquake
- Recover
- Scald
- Protect
Quagsire's on the team for basically one reason—to beat Zacian-Crowned, who can only ever 3HKO Quag (even after stealth rock damage). Play Rough hits Quag the hardest (40.4-47.5%), so if the opposing ZC has Play Rough, it's important to make sure that Quag stays healthy and doesn't lose his leftovers, which would make switching in on ZC with rocks much scarier. Use recover liberally to ensure that Quag stays healthy when he's forced out. Basically, you're in no rush to kill ZC as long as you have Quag. Unaware is absolutely mandatory, as it's the only reason Quag can beat ZC. Leftovers could probably be replaced with Heavy-Duty Boots, but I like having the passive recovery with protect. 248HP EVs gives Quag an odd-numbered HP without reducing his effectiveness against ZC. 252 Def and a relaxed nature ensure Quag can effectively wall ZC. Since I run Scald and Earthquake, I run with a relaxed nature so neither of the moves is unnecessarily weakened. (Quag barely outspeeds anything in AG anyway, let alone ZC.) Earthquake hits ZC for 51-61% and Scald is there to chip away and potentially burn ZC or whatever switches in on Quag, which is often Yveltal. It is almost mandatory to keep Quag alive and healthy, as the rest of the team doesn't fare well against ZC. That said, a very unhealthy ZC can be taken down by Lugia, but Lugia can't safely switch in on ZC so something else would have to be sacrificed, which isn't ideal. Quag can also be a useful tool for controlling a number of boosted physical attackers, e.g., ESpeed Swords Dance Arceus and Weakness Policy Necrozma DM.
+1 252+ Atk Zacian-Crowned Play Rough vs. 248 HP / 252+ Def Unaware Quagsire: 159-187 (40.4 - 47.5%) -- guaranteed 3HKO after Leftovers recovery