OKay. I am fairly new to Ubers -- I play OU most of the time, I just thought up a few Legendaries from the games I played. I tried to give them movesets and put my knowledge of the OU metagame into Ubers. Hopefully it works.
1
Xerneas @ Power Herb
Ability: Fairy Aura
EVs: 252 SpA/ 252 Spe / 4 HP
Timid Nature
- Geomancy
- Moon Blast
- Focus Blast
- Thunderbolt
Xerneas is my setup sweeper. It will lead most of the time, otherwise it will try to get a revenge kill if Deoxys-Speed is too risky or unavailable.
2
Groudon-Primal @ Red Orb
Ability: Desolate Land
Shiny: Yes
EVs: 128 Def / 252 Spe / 128 HP
Adamant Nature
- Precipice Blades
- Return/Thunder Punch
- Iron Head/Fire Punch
- Hone Claws
or
Groudon-Primal @ Red Orb
Ability: Desolate Land
Shiny: Yes
EVs: 252 SpA / 252 Spe / 4 Spe
Modest Nature
- Earth Power
- Flamethrower/Eruption
- Solar Beam/Thunder
- Rock Polish
I wasn't sure which moveset to go with for Primal Groudon. Groudon is mostly physical, but it has better special coverage. I was debating on using Trick Room with Deoxys-Defense because it can't learn that for some reason, so I just grabbed Rock Polish to break Primal Kyoger's Speed tie.
3
Mimikyu @ Focus Sash
Ability: Disguise
EVs: 252 Atk / 252 Spe / 4 HP
Jolly Nature
- Play Rough
- Shadow Sneak
- Drain Punch
- Swords Dance
I LOVE Mimikyu. Everywhere I go, I want to bring it, but I can't take it out of OU because it's barely afloat in there. But in Ubers, there are lots of Psychic types and Dragon types, so it will sky rocket.
4
Kyurem-White @ item
Ability: Turboblaze
EVs: 252 Spe/ 252 SpA / 4 HP
nature Nature
- Fusion Flare
- Ice Burn
- Earth Power
- Roost
I didn't know what to fill in here. So I grabbed Kyurem-White. It's a common Mon, not widely used, but I thought it might get a kill if I'm lucky. If there is a better replacement, please shoot me one.
Necrozma-Dusk-Mane @ Ultranecrozium Z
Ability: Prism Armor
EVs: 4 HP / 252 Atk / 252 Spe
Jolly Nature (+Spe, -SpA)
- Photon Geyser
- Earthquake
- Sunsteel Strike / Stone Edge
- Swords Dance
*I took the advise from sumwun and added Necrozma and Deoxys Attack.*
6
Deoxys-Defense @ item
Ability: Pressure
EVs: 252 SpA / 128 Def / 128 HP
Bold Nature
- Toxic
- Protect
- Recover
- Psycho Boost
Or
Deoxys-Attack @ item
Ability: Pressure
EVs: 252 Spe / 252 Atk / 4 HP
Jolly Nature
- Drain Punch/Super Power
- Zen Headbutt
- Knock Off
- Thunder Punch/Rock Slide/Poison Jab