Every guide I’ve found which tells one how to access the Ruin Depths in the Calm Lands is wrong! They all show some elaborate method for unlocking it which includes sending L5 birds 1, 2, and 3, then 2, 3, and 4, then 1, 3, and 4, then 1, 2, and 4, after sending 4 of each previous level out. And they always insist that you must send them ALL to the Calm Lands.
Here’s why it’s bullshit:
1. You can send them anywhere you’d like.
2. You need only send four of each level (maybe fewer, I haven’t tried fewer) – once the four L5s return, exit and reenter the ranch. Boom – the Depths are now open.
*. You also only need to fight 7 battles between batches.