In the initial release of Shield, only three Legendary Pokémon were available. However, through the Isle of Armor and Crown Tundra DLC, many more Legendaries and one Mythical entered the franchise. These quickly proved to be very strong and capable of carrying players through the games.
Some Pokémon become stronger by combining with others, but here, each Legendary or Mythical's power will be evaluated based on its capability as an individual. Because of their stats, Abilities, available moves, etc., certain Legendary and Mythical Pokémon are better than others when it comes to playing through the Pokémon games.
Calyrex
When combined with Glastrier or Spectrier, Calyrex becomes much stronger and is among the best in Galar. On its own, though, Calyrex is much weaker, which is important to its story in the Crown Tundra DLC. Each of its stats shares the same unimpressive value, except for its HP, which is slightly higher.
It does have access to some great Grass and Psychic attacks, but it does not have good coverage options through leveling up. It makes sense for its story that it would be weak without its steed, but this does not make Calyrex any more desirable by itself in combat.
Regidrago
Under the proper circumstances, Regidrago can be great. Its signature move, Dragon Energy, bases its power off of its current HP, and when Regidrago is at its maximum HP, it is one of the most powerful Pokémon Dragon moves. The Legendary's fair Special Attack also helps to make this move stronger. However, Regidrago is not fast enough to out-speed many opponents, especially at higher levels.
Its defensive stats are both terrible, so its health suffers from one reasonable hit. As a result, Regidrago's strongest move quickly becomes unusable. It has some other Dragon-type attack options, but its offensive stats are not high enough to make these exceptional, even with the assistance of its signature Ability, Dragon's Maw, which buffs Dragon-type moves.
Urshifu
Urshifu has its strengths and weaknesses in both its Single Strike Style and its Rapid Strike Style. The former has three type-weaknesses, but only three resistances. The latter has five type-weaknesses, but seven resistances. Both forms share the same stat spread, with a great Attack stat, but an unfortunate Special Attack stat.
Every attacking move they can learn by leveling up is Physical, but they run into trouble if their opponent resists these strikes effectively. In addition, their HP and Defense are solid, but their Special Defense is poor, which can cause problems.
Galarian Articuno
The Galarian variant of Articuno has a rather high Special Attack stat, which can then benefit from its Ability, Competitive, which boosts its Special Attack when an opponent lowers any of its stats. Galarian Articuno's Special Defense is capable, but its Defense is less impressive.
Almost all of its available attacks through leveling up are Psychic-type, though it does have a few other options. The strongest of these is Hurricane, which, while powerful, is not always accurate. It can often out-speed enemies, but if it cannot, Physical attackers can cause issues.
Galarian Zapdos
In its Kantonian variant, Zapdos has remained one of the best dual-type Electric Pokémon since its introduction, and the Fighting/Flying-type Galarian Zapdos lives up to the status of its other variation. Its solid Speed stat often lets it move first, and its Attack stat helps it to capitalize. Its Ability, Defiant, also works similarly to Competitive, but instead, it powers up Zapdos's Attack.
Like Galarian Articuno, almost all of its level-up moves fit its superior attacking category, which can make battles against foes with high Defense difficult, as it has no way to work around it. Its defensive stats are equal in value, but they are not great.
Galarian Moltres
Galarian Moltres's Defense is able, and its Special Defense is fantastic. This allows the Legendary to withstand extensive damage, and its Ability, Berserk, helps it dominate. This boosts Moltres's Special Attack when it reaches below half of its maximum HP due to an attack.
Trainers can use this by healing Moltres after Berserk activates and repeating the process, powering up its Special Attack to a significant extent. Unlike its counterparts, Moltres has several move options for its less powerful offensive stat, so it can use decent Physical moves if need be.
Zarude
Fairly fast and capable of hitting hard with its high Attack stat, the Dark/Grass Mythical Zarude can be effective in battle. Its move pool is slightly lacking, with the only Dark-type attack it can learn through leveling up being Bite.
Zarude's typing complicates things. While it resists six types, it is weak to seven, one of which is an extreme vulnerability. Its solid bulk helps it to an extent, though. Its signature move, Jungle Healing, helps it recover some HP, but the number of weaknesses can be troubling.
Spectrier
The pure Ghost-type Legendary has the stats to be an excellent Special attacker. Its Speed usually allows it to strike first, but its limited number of Special options is concerning. The only level-up Special attacks it can learn are Hex and Shadow Ball, and its other attack options use its mediocre Attack stat. If an opponent does not resist Ghost, Spectrier is incredible.
Its Ability, Grim Neigh, powers up its Special Attack when it defeats a Pokémon, which makes it an offensive powerhouse on the Special side. Its defensive stats are lacking, but its swift and powerful strikes make them often unnecessary.
Glastrier
Glastrier is capable of taking immense damage, which is useful because its low Speed stat leaves it almost always moving last. Its Special Defense is solid, and both of its Physical stats are fantastic. In addition, its Ability, Chilling Neigh, raises its Attack when Glastrier knocks out a Pokémon.
Its Special Attack is underwhelming, but with how high Glastrier's Attack stat is, it can often even overcome great Physical defenders. Unfortunately, it only resists one type while being weak to four, but its defensive stats are enough to make it a tank.
Regieleki
As the fastest Pokémon currently in existence, Regieleki can devastate before opponents have the chance to move. Its offensive stats are equal but not excellent by Legendary standards. However, its Electric attacks get a significant boost with its Ability, Transistor.
Regieleki's defensive stats are terrible, and its HP is unimpressive, but with its Speed and power, it can dominate, as long as its attacks are not heavily resisted. These factors are what make Regieleki possibly the strongest pure Electric-type Pokémon.
