Unown and Entei
My son told me that in the movie Entei turned up when the professor's daughter made a wish to Unown. Do we need to find all the Unowns before we can catch Entei?
There are 26 letters plus 2 symbols of Unown? i've seen a couple in gyms but so far seen none in wild.
Answers
I think the Gen2 legendary beasts would be easier to implement than the Gen1 Legends.
In Gold/Silver (spoiler alert?), after you wake up the legendary beasts, they run off into the wild. They then continually move around the mapand you need to get lucky and meet up with one of them on the same route as a wild encounter. Except, like Abra, you only have one turn before it immediately flees and and you have to track it down again.
For Pokemon Go, they could have one legendary beast spawn in a city for a week with the same IVs and moveset. Every hour or so it would spawn in a different area. Like Abra, you get one chance to catch it before it runs. If it runs from you, it would continue to spawn in new areas in the city for the rest of the week. After you catch it, that particular copy of the legend would stop spawning for you.