Hi! I'm not too experienced with UU, but I'm knowledgeable enough to have an idea of top-tier threats for UU and other pokemon that you'd need to be wary of. The first issue I see is that you have 3 dragon types on the team and not much to deal with Dragon weaknesses, which means that the team has a huge weakness to opposing Dragon, Fairy, and Ice type pokemon. Also, Umbreon is being used as a blanket check for a lot of pokemon which puts a ton of pressure on it, and if you lose Umbreon, you pave the way for a bunch of set-up sweepers and Choice Scarfed/fast pokemon in general to come in and break through the rest of your team. Furthermore, you have no hazard setter or hazard removal. Not having a hazard remover isn't the worst thing to happen to a team (although I am adding one with the changes since the final team becomes a bit less offensive), but having a hazard setter is something that is important to fit onto a team whenever necessary (which is most of the time).
The choices that you have available for an in-game competitive team don't really help with the problems I mentioned, so it won't be the most viable team you could have. If I were to suggest something based on what you have, it would probably be to add Blastoise as a 6th pokemon and make its moveset Scald / Rapid Spin / Roar / Toxic so that you have a hazard removal for Salamence, since it takes 25% damage from Stealth Rock every time it switches into it. If you want to use a much better team with the changes I'm going to suggest (I'm not sure if you have the pokemon I'm suggesting as replacements since they're not on your list), then I recommend using Pokemon Showdown, which is a website that allows you to build teams and battle against other players without being restricted by the pokemon you have available in-game. I'm assuming you're pretty new to competitive pokemon, so I'll try to explain my changes as in-depth as I can so you can understand my reasoning for making them. If you're confused by anything, feel free to let me know and I'll try to help clear that up.
Now, onto the changes. I'm going to keep Mega Sceptile as your only dragon type pokemon because it's your mega and it's a really powerful pokemon in the tier (Salamence is really strong in UU as well, but if I replace Mega Sceptile, I'll have to look for a new mega pokemon that works, which might cause me to have to change the entire team, which I don't want to do). Mega Sceptile appreciates having Fairy types such as Florges removed because they can take a hit and kill it with their Fairy type moves. In order to have something to take on fairy types, I suggest replacing Salamence with Crobat.
Crobat @ Sky Plate
Ability: Infiltrator
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Brave Bird
- U-turn
- Cross Poison
- Defog
This offensive Crobat set hits Fairy and Grass types really hard with its Flying and Poison type moves, which is great for Mega Sceptile as I said earlier. Adding Crobat also gives you a hazard remover with Defog, which is pretty helpful for the team because your pokemon will likely be switching around a lot, racking up damage if hazards are up. U-Turn is a nice move that allows it to switch out if you predict that the opponent is going to bring in a Crobat counter, which allows you to safely switch into something that can take on that pokemon.
Next, I want to have something that can take pressure off of Umbreon. Umbreon is your only switch-in to a lot of pokemon in the tier, which means that it's taking a lot of damage over the course of the game. You also have no safe switch-in to certain Fire type pokemon such as Infernape and Choice Scarf Darmanitan. To help take on Fire types and take on hard-hitting attackers alongside Umbreon, I suggest replacing Haxorus with Suicune.
Suicune @ Leftovers
Ability: Pressure
EVs: 252 HP / 252 Def / 4 SpD
Bold Nature
- Calm Mind
- Scald
- Rest
- Sleep Talk
This Suicune set is a great way to win games versus stall teams (I don't know how prevalent they are in UU, but I'm sure they exist). Scald is the typical move to click when its counters are still up, allowing it to get some damage off on whatever switches into it and it can potentially burn things which can wear pokemon down even more. The set revolves around boosting with Calm Mind once its checks and counters are eliminated and using the combination of Rest and Sleep Talk to stay healthy and continue to boost or attack with a boosted Scald. Before those checks and counters are gone, it's still great at checking a lot of physical attackers that can take on Umbreon and the rest of the team in general.
Looking at the team with the current changes, we don't have a hazard setter which I definitely want to add on this team. The team doesn't look overly annoyed by anything, but as I said in the opening paragraph, I'm not that experienced with UU so I could be overlooking something. One thing I noticed was that Grass Knot Infernape could be troubling since it has the chance of 2HKOing Suicune from full health with Grass Knot, but we have Crobat to revenge kill it so I'm not too worried about it. I didn't want to add a Stealth Rocker that was a Water or Steel type because I thought that having a second Water or Steel type would be a bit troubling when it came to those types' respective weaknesses. I decided on adding Focus Sash Lead Mamoswine as your 6th pokemon.
Mamoswine @ Focus Sash
Ability: Oblivious
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
- Stealth Rock
- Ice Shard
- Earthquake
- Icicle Crash
This set ensures that Mamoswine can live any hit that can OHKO it and set up Stealth Rock. Mamoswine can also be preserved if it's a good pokemon against the opponent's team. This set has Oblivious over Thick Fat as its ability because it makes sure that Mamoswine isn't affected by Taunt, which further helps it set up Stealth Rock. Ice Shard is a great priority move which can potentially be used to revenge kill something. I opted for Icicle Crash over Knock Off or Endeavor because I felt that it would help Mamoswine be more offensive instead of being used to get up Stealth Rocks and be taken out by something. I don't think Endeavor is that useful because it's mostly noteworthy against bulky Water types, which this team can handle well. Knock Off is a potential move you could use over Icicle Crash if you think removing items from pokemon are more important for this team. I chose to use Jolly nature over Adamant because it outspeeds Adamant Heracross. Choice Band Heracross can be a threat because it 2HKOs Suicune with Close Combat, and they typically run Adamant nature. By using Jolly Mamoswine, you get an extra revenge killer to it. However, if you're not finding Choice Band Heracross to be a threat, then you can run Adamant nature on Mamoswine for extra damage.
For the remaining pokemon, here are the sets that they should be running.
Your Sceptile set is good with the moves you plan on giving it. I prefer Giga Drain over Energy Ball, though because it helps it recover HP. It's personal preference, though. Also, the 4 HP EVs should be moved to Special Defense because removing those HP EVs makes sure that Mega Sceptile has an odd HP number, allowing it to switch into Stealth Rock one extra time.
For Umbreon, its Attack stat is really low so I don't like the idea of a Curse set. AWildNoobAppeared! is right by suggesting Foul Play over it. This is the set that Umbreon should be using:
Umbreon @ Leftovers
Ability: Synchronize
EVs: 252 HP / 4 Def / 252 SpD
Calm Nature
- Wish
- Protect
- Heal Bell
- Foul Play
This is a great support set for the team. Wish + Protect allows it to recover HP relatively safely. Wish can also be used to heal up any weakened pokemon on the team. Heal Bell is good for removing any status infliction on your team. Foul Play is used to deal damage. It hits physical attackers such as Mega Aerodactyl really hard. Protect can also be used to scout for a certain move or a Choice item on a pokemon.
Finally, for Lucario, I think that the Swords Dance physically attacking set is better than a Calm Mind/Nasty Plot set. Lucario has a lot more physical moves than special moves that it can use, and I just personally think that it's the stronger set in the UU metagame. There are a lot of options that Lucario has for the Swords Dance set, but I think this one has the best coverage for the team.
Lucario @ Life Orb
Ability: Justified
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Swords Dance
- Close Combat
- Extreme Speed
- Crunch
I chose to use Extreme Speed because it hits more things than Bullet Punch, plus Extreme Speed is stronger. The Steel type coverage isn't too necessary in my opinion because the main things it hits are Fairy types, which are covered by Crobat; and Mega Aerodactyl, which is covered by Suicune and Umbreon. Extreme Speed is also nice because its +2 priority means that it outspeeds +1 priority attacks, such as Mach Punch, that can kill it. I chose to use Crunch because Choice Specs Chandelure could be annoying because it can cripple Umbreon, the main check to it, by using Trick to give Umbreon a Choice Specs. Crunch hits Chandelure for super effective damage, making it less annoying to deal with. Jolly Nature is preferred over Adamant for this team because Jolly Lucario outspeeds Timid Chandelure, which most Chandelure sets are. Some other options it can have are Ice Punch and Earthquake, but I felt that Mamoswine covered both of those, and hitting Ground types with Ice Punch wasn't necessary since you have Mega Sceptile and Suicune. Furthermore, it gives you a decent answer to Celebi. Outside of Earth Power on offensive sets and Thunder Wave on the support set (which isn't that bad since Umbreon has Heal Bell to remove paralysis), it can take anything from Celebi and can 2HKO it with Crunch after Celebi's been weakened a bit. It also has a chance of OHKOing if you use Swords Dance once.
Sorry it took me 5 days after you posted this to come up with an answer, I didn't really look at it too much when it was posted since I'm not an experienced UU player. If you do end up using Pokemon Showdown, good luck on the UU ladder! Just in case, I'll leave an importable of this team so that all you have to do is copy/paste the team into Showdown instead of going back and forth between the teambuilder and this post.
Summary of Changes
>
>
as 6th pokemon
Giga Drain>Energy Ball; 4 HP EV-->SpD
change set
change set
