Pokemon GO's newest event is the Team GO Rocket Celebration Event, causing players to meet members of this villainous team far more often in-game. Among all of the weak grunts, players will also be encountering the various leaders of Team GO Rocket.

Sierra, like the other Team GO Rocket Leaders in Pokemon GO, can be quite the challenge for unprepared trainers. Unlike the less experienced grunts, Sierra uses far more powerful Pokemon and can take advantage of Protect Shields just like players.

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While Sierra's first Pokemon on her team will be the same no matter what, her second and third party members can be any out of three specific Pokemon. This lineup will change with every encounter with her, making her a bit unpredictable. If players rematch her within the same encounter, Sierra will have the same Pokemon lineup as she did in the previous match that players lost to.

Sierra's first guaranteed party member is Carvanha, a dual Water and Dark-type Pokemon. Its typing makes it weak to Fairy, Bug, Electric, Grass, and Fighting-type moves. While it may have a lot of weaknesses, Carvanha also has even more resistances with it resisting Ghost, Steel, Water, Ice, Dark, Fire, and Psychic-type moves.

There are quite a few Pokemon that can be used to help take this Pokemon down without losing too much health in the beginning of the battle. The Pokemon that are most recommended are:

• Machamp - Counter and Dynamic Punch
• Raikou - Volt Switch and Wild Charge
• Sirfetch'd - Counter and Close Combat
• Zapdos - Thunder Shock and Thunder Bolt
• Alakazam - Counter and Dazzling Gleam

One of Sierra's possible second party members is Hippowdon, a pure Ground-type Pokemon. Hippowdon's typing makes it weak to Grass, Ice, and Water-type moves. It however also resists Rock, Poison, and Electric-type moves.

While it may seem obvious what to use against Hippowdon, Sierra can have this Pokemon outfitted with certain fast moves that can make things much more difficult. This Pokemon will either have Fire Fang, Ice Fang, Thunder Fang, or Bite as its fast move.

If Hippowdon is using Fire Fang or Ice Fang, players should use:

• Kingler - Bubble and Crabhammer
• Kyogre - Waterfall and Hydro Pump
• Crawdaunt - Waterfall and Crabhammer
• Sharpedo - Waterfall and Hydro Pump
• Swampert - Water Gun and Hydro Cannon

If Hippowdon is using Thunder Fang or Bite, players are recommended to use:

• Galarian Darmanitan - Ice Fang and Avalanche
• Roserade - Razor Leaf and Solar Beam
• Black Kyurem - Dragon Tail and Blizzard
• Mamoswine - Powder Snow and Avalanche
• Weavile - Ice Shard and Avalanche

Another possibility for Sierra's second team member is Porygon-Z, a pure Normal-type Pokemon. Playing against its weaknesses can be difficult due to it only being weak to Fighting-type moves, but it also only resists Ghost-type moves.

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When dealing with Porygon-Z, players are recommended to use:

• Lucario - Counter and Aura Sphere
• Conkeldurr - Counter and Dynamic Punch
• Breloom - Counter and Dynamic Punch
• Machamp - Counter and Dynamic Punch
• Blaziken - Counter and Focus Blast

The last possible Pokemon Sierra can use as her second Pokemon is Mismagius, a pure Ghost-type Pokemon. Mismagius's typing makes it weak to only Dark and Ghost-type moves while also resisting Bug, Poison, Fighting, and Normal-type moves.

While Mismagius is weak to Ghost-type moves, using Ghost-type Pokemon isn't really recommended due to Mismagius mostly using Ghost-type moves itself. Because of this, it may be on the wiser side to stick to Dark-type Pokemon. Some of these include:

• Mega Houndoom - Snarl and Foul Play
• Tyranitar - Bite and Crunch
• Weavile - Snarl and Foul Play
• Darkrai -Snark and Shadow Ball
• Hydreigon - Bite and Dark Pulse

One of Sierra's possible third and final Pokemon is Houndoom, a dual Dark and Fire-type Pokemon. Houndoom's typing makes it weak to Fighting, Ground, Rock, and Water-type moves with it also resisting Steel, Ghost, Grass, Ice, Dark, Fire, and Psychic-type moves.

Luckily for Pokemon GO players, Sierra's Houndoom cannot mega evolve into Mega Houndoom. It still has great potential to be a threat though, so players are recommended to use:

• Rampardos - Smack Down and Rock Slide
• Kingler - Bubble and Crabhammer
• Therian Landorus - Rock Throw and Earth Power
• Conkeldurr - Counter and Dynamic Punch
• Kyogre - Waterfall and Hydro Pump

Another possible final encounter in the battle with Sierra is Flygon, a dual Ground and Dragon-type Pokemon. It is weak to Ice, Fairy, and Dragon-type moves with it resisting Rock, Poison, Fire, and Electric-type moves.

While some players may be eager to bring out their powerful Dragon-types, it may not be a good idea. Sierra's Flygon can have either Mud Shot or Dragon Tail as its fast move, making it able to also deal high amounts of damage toward Dragon-types if players are unlucky.

If Flygon has Dragon Tail for its fast move, players are recommended on using:

• Galarian Darmanitan - Ice Fang and Avalanche
• Mamoswine - Powder Snow and Avalanche
• Weavile - Ice Shard and Avalanche
• Glaceon - Ice Shard and Avalanche
• Jynx - Frost Breath and Avalanche

If Flygon instead has Mud Shot for its fast move, players can still use the above Pokemon. However, it will become safer to use:

• Black Kyurem - Dragon Tail and Blizzard
• White Kyurem - Dragon Breath and Blizzard

The last Pokemon left to Sierra's disposal is Walrein, a dual Ice and Water-type Pokemon. It is weak to Fighting, Rock, Electric, and Grass-type moves while only resisting Water and Ice-type moves.

While Walrein's many weaknesses and few resistances may make it seem like a cakewalk to deal with, it has the same obstacle as many of Sierra's other Pokemon. This of course is the different fast moves that Walrein can have, making players require different recommended Pokemon based on this move.

Walrein can either have Waterfall or Ice Breath as a fast move. If Walrein has Waterfall, players are recommended to use:

• Cradily - Bullet Seed and Grass Knot
• Chesnaught - Vine Whip and Super Power
• Tangrowth - Vine Whip and Power Whip
• Alolan Exeggutor - Bullet Seed and Seed Bomb

In the case of Walrein having Ice Breath for its fast move, players are instead recommended on using:

• Aggron - Smack Down and Stone Edge
• Armaldo - Fury Cutter and Rock Blast
• Mamoswine - Mud-Slap and Ancient Power
• Probopass - Rock Throw and Rock Slide

Pokemon GO is available on Android and iOS.

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Source: Pokemon GO Hub and Pokemon GO Info