In Pokemon Sword
will be battled near the end of the Post Game
. It will actually be the strongest Wild Pokemon
found in the entire game, being at an astonishing Level 70. If that doesn't make it difficult enough to capture, it's ability will see it receive a boost to its Attack
Stat immediately when the battle begins. It will even know the move Swords Dance that can further escalate its Attack Stat, making it a sweeper like no other!
Obviously, the easiest way to capture to Zacian
would be to use the Master Ball
you receive from Magnolia
on it. Master Balls guarantee a Pokemon Capture, meaning you'll catch Zacian no matter what it you use it. It would be especially wise to use the Master Ball on Zacian since you won't receive the item until the Post Game
anyways, long after you have already captured Eternatus
. Furthermore, there won't be another Pokemon as strong as Zacian after you do catch it, so there's really no point in not using the Master Ball on it.
But should you not want to use your Master Ball
on it for some reason, you can always paralyze it in battle by using Thunder Wave, lower it's Hit Points
as low as possible without causing it to faint, and then use loads of Ultra Balls until it's captured. This is the oldest and best known way to catch any Pokemon, and it still works to this very day. If you do choose to use this method, however, remember to always save your game before facing Zacian
just in case you do accidentally cause it to faint in battle.