I have both Tornadus and Thundurus in my party. I went to Abundant Shrine..

This happened to me too but I knew what was wrong do have a tornadus or thundrus that is originally yours??

I know the exact problem, Landorus is #645 on Pokemon White, but on Pokemon Black, you must meet him by GTS only before you can fight him, now I have a question for you, answer as soon as possible, do you have Pokemon White that you are trying to catch Landorus on, or Pokemon Black, because it does make a difference, Pokemon Black Pokedex # before GTS Trade, ---, nothing, he isn't loaded into Pokemon Black automatically, he is in Pokemon White, without the trade, #645 is Kyurem( Will tell in next post if you don't know what he is), so, in Conclusion, you must trade a Pokemon for the guy that is offering Landorus, (Must go on GTS Negotiations, not GTS because GTS searches for Pokemon trainers that are offering already obtained or seen Pokemon, and just to let you know, when you go on GTS Negotiations, when you look at what he/she offered, it is not added to your Pokedex, you must finish the trade.) Then you may catch Landorus in Abundant Shrine, go up the steps, etc., etc., but you have to have Tornadus and Thundurus in the first 2 spots in your party, (left to right, up to down, not up to down left to right) like so.

1 2
3 4
5 6

And when you click the shrine then it will show a "!" above your head and when you press "A" it will say "Thundurus and Tornadus are struggling in their Poke-Balls!" and you take a step backward and Landorus falls from the sky, and just like any other Stagnant (Doesn't Move) Pokemon/Legendary Pokemon Press "A" it makes a Roar, and the wierd "KYYUUUHHUHHHH" That every Legendary Pokemon makes, then it makes a shiny sparkly effect and it says "A Wild Landorus appeared!!!!" If you have your Master Ball Still, I would say save it for a shiny, but he has the lowest Catch Rate Of All Legendaries (CRAL)and is the only Legendary Pokemon to have a Gender (7/8 to be Male when you encounter it, 1/8 to be Female when you encounter it.

Sorry for the Long Post, Your Friend, Anonymous.

Wait, so in Pokemon black, the thundurus has to be you as it's original trainer? Because if thats true, that sucks because my original thundurus is lost in gts......... Are you sure there isnt any other way to interact with the shrine with both Pokemon that arent yours?

For lucario is cool the only other way is to get the action replay code to rebattle Thundrus thats how I solved my problem...

Well you have to get at least one by yourself and one from trade. That's what I did. Hope this helps

Ok. Honestly that dude's talkin bull. All you need to do is have 1 of your own and the other from a trade. They MUST be with you. It doesn't matter where they are in your party either so long as you have em. You don't need to go on gts or any of that. I know because I JUST caught mine 20 minutes ago