Catch Latios/Latias
A good team to catch Latios/Latias is Grovyle(or Sceptile), Altaria, and Golbat. You can get Altaria at Sky Pillar at level 39. Level it up to 40 and then go to the move tutor in Fallabor Town.
Use a heart scale (found underwater on routes 126 and 124) to teach it sing. Then get a Golbat at Victory Road at level 40. Level it up until it learns mean look at level 42.
Level up Grovyle/Sceptile until it learns false swipe. Grovyle learns it at level 53 and Sceptile learns it at 59. Give Grovyle/Sceptile the quickclaw then go find Latios/Latias and use false swipe. It will put its’ health to 1hp.
After you cut down Latios/Latias health, put the sucker to sleep. Next time you find it, Use Alteria’s sleep move. Again, make sure you equip quickclaw. After it’s asleep it will run… again! If you going to capture Latios/Latias, you’ve got to stop it from running.
That’s where Golbat comes in. Equip it with quickclaw and find Latios/Latias. Use mean look to keep it from running. Next have a couple of Ultra balls handy to capture it with.
With Latios/Latias on low health, asleep, and not able to run, you have a 90% chance of success.
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