Latios:
(M) @ Cheri Berry
IVs: 31/x/31/31/31/31
EVs: 252 SpA / 78 SpD / 180 Spe
Ability: Levitate
Lvl: 100
Modest nature
-Psychic
-Ice beam
-Thunderbolt
-Memento
Latios is the best possible lead for the Arena without a doubt. The plan with Latios is simple: just sweep. 9 times out of 10 Latios will be able to tear through the opposing team by one hit KOing or two hit KOing most of the arena's threats, while surviving most things that aren't super-effective (and some things that are). Psychic, Ice beam, and Thunderbolt simply supply the best coverage. Testing with things like HP fire, Dragon claw, and HP grass it becomes clear that these three moves can simply do the same things as any other set, in two hitting most things. As said above, if this can sweep there is no reason to stop that by hitting memento. That being said anything that walls latios or will likely OHKO it memento is a fantastic move. There is very little that can take a chunk out of second mon Snorlax at -2, nonetheless stop it from setting up a curse and knocking it out in two hits subsequently.
180 speed is all you need to beat out the base 100 speed tiers that are present in arena, and anything that is faster is OHKO'd with very few exceptions. Only thing worth looking out for is some Electrodes that carry Mirror coat, but they can be easily neutralized by just Thunderbolting first then hitting Psychic. Rest of the EVs go into SpD to just give it a little more survivability to finish off things that take three hits and tank an Ice beam. It's best in SpD vs. HP because there are no physical threats to Latios that won't OHKO it anyways, better to just take less from super-effective special attacks.
The biggest change that's present here is the use of Cheri Berry over what is commonly brightpowder, twistedspoon, or similar. There are a LOT of twave, body slam or otherwise paralysis users in the Arena, ALOT. The Cheri Berry forces them all to hit twave twice and practically guarantee a loss in judging. This is particularly useful against several electric types or things like Registeel which Latios would otherwise lose to or take more than one hit to kill. Even if I wasn't running Lum Berry elsewhere on the team I would still recommend running Cheri, sleeper item pick for sure.
Latios was obtained with the Battle Tower trick in Ruby using the roamer to get perfect IV's.
Snorlax:
(M) @ Leftovers
IVs: 31/31/31/x/31/31
EVs: 252 HP / 252 Atk / 4 Def
Ability: Thick Fat
Lvl: 100
Adamant nature
-Curse
-Shadow ball
-Earthquake
-Selfdestruct
I wouldn't call Snorlax the star of the team but it does seem to put in the most work. This is pretty standard stuff based on the leading Latios set. Again, 9 times out of 10 Latios will get enough work done for easy cleanup for Snorlax, and if it doesn't, Snorlax comes in against a -2 pokemon that will inevitably die to unboosted or 1 curse Lax.
EV's and nature are pretty standard, special mons, especially at -2 don't stand a chance at breaking through Lax. I've tested with some defensive or special defensive investments, but Lax shines with the big HP stat and needs all the attack to get some KOs due to not running a normal STAB. The standout part of this set is the crazy strong Selfdestruct.
Selfdestruct on Snorlax is the strongest unboosted attack in the game. It is seriously unreal how powerful it is, Slaking Hyper beam can't even compare. I won't post calcs here but I recommend just checking them out and seeing the damage it can do to things like Skarm, Wobbuffet, Etc. It makes explosion on things like Metagross and Gengar look pathetic. This synergizes so beautifully with the Latios lead that can kill most teams on its own. Probably around 250+ of the games in this streak are Latios sweeping into Snorlax blowing up.
Selfdestruct is a XD move tutor move that Snorlax can learn. Lots of people don't know this because most PKMN resources don't list Lax as able to learn it, but it can and it's amazing.
Snorlax should avoid setting up unless it is out against the opponent's lead or a second mon that makes it free. Examples being Wobbuffet, Counter Swampert, and CurseLax. You're always better off just trying to kill whatever is out because the incredible Selfdestruct will annihilate the 3rd 95% of the time - and if it doesn't the last mon is specifically designed to always beat weakened PKMN.
It's also worth noting that while I used a male snorlax in my streak, female Snorlax avoids more attract mons than the male one does, hence making it the better option if possible, but to RNG one that has the right nature, IVs, ability, and gender can get old (assuming you want to do it all on cartridge).
Snorlax was obtained using egg IV RNG in Emerald with a 3 IV ditto and I think 3 different Snorlax.
Latias:
(F) @ Lum Berry
IVs: 31/6/31/30/31/30
EVs: 128 HP / 202 SpA / 180 Spe
Ability: Levitate
Lvl: 100
Modest nature
-Psychic
-Ice beam
-Thunderbolt
-Hidden Power Fire
To complete the sandwich is Latias on the other end. Latias is a weird one, and only really barely outperformed other PKMN that I tested such as Suicune, Slaking, Tauros, Etc. At the end of the day Latias does a very similar job that Latios does, just instead of sweeping it is on cleanup duty. Whatever Latios and Lax can't take out falls on Latias to finish off. The thing about Latias is simple, but important.
YOU NEVER WANT TO BRING OUT LATIAS. Latias is not made on this team to sweep or beat several mons. It can and will do that if it has to, but should be avoided at all costs. If you come down to Latias on this team, especially out against the second opponent mon, you should be very afraid of what comes after, it lacks the firepower and survivability to either win or get to judging. Generally though, this is designed to take out stuff at low health or nab quick OHKOs with super-effective attacks, hence moves like HP Fire.
Moveset is very obvious, best coverage possible. EVs are to maximize bulk while still getting important OHKOs on things like heracross, that can easily take you out. The HP Fire on Latias is important beyond the expected Forretress and Scizor, it is absolutely necessary for taking out Mirror coat users without getting blasted by PKMN such as Swampert, Tentacruel Milotic, and Blastoise. Dive is also a move I considered on this set, to try and kind of cheat your way to win judging, but things like Gold Greta's Shedinja are just too inconsistent. The IVs on this set are basically the best I could get while still getting 70 BP HP Fire on Latias.
Latias was obtained in Emerald on Southern Island using the Battle Record frame skip, Method 1 RNG abuse on stationary and the Pomeg Glitch to get the Eon Ticket.
![IMG_20210216_225807[1].jpg](/forums/media/data/attachments/316/316395-b4c33130ffc83ce3ef8482730d183db6.jpg "IMG_20210216_225807[1].jpg")
Banded Normal types are a nightmare for this team since I got no resistances or immunities to their moves. The worst part is that Granbull gets a guaranteed kill depending on what it chooses since it could pick either Shadow Ball or Mega Kick with the latter breaking Blissey's eggs into smithereens.
It's a troublesome Pokemon on Singles since I got no Steel type resist on the team either. Usually Blissey is sacked to land the OHKO with Earthquake. Extremely bad news if it leads on a non-healing battle. On Doubles, it's not so threatening since you can double target it. (Guts boosted Earthquake will OHKO any set)
Deserves a special mention since it destroyed my last two attempts. Aggron 1 has Quick Claw and access to Aerial Ace to end Heracross and neither Blissey or Latios appreciate taking Iron Tail. No Iron Tail resistant switch-in makes this mon extremely painful unless it misses.
Dangerous if Set 2 gets an Ancient Power boost, but relatively harmless if it's locked on anything else.
Explosion with Ghost type is a pretty dangerous combination and with the lack of Protect, it can be deadly if unchecked. To make matters worse, all Golem needs is a Quick Claw activation to completely fuck you over.
+ 
or 
Latios6, Regirock6,