[Script] [FireRed] How to get legendary static encounters to appear after checking certain flags

[robertussan]

I'm currently working on a ROM hack of Fire Red to suit my own wants and wishes, and I'm trying to get the Legendary Beast (Entei, Raikou, and Suicune) to appear in certain places after the player has defeated the Elite Four the first time around. For instance, I want Entei to appear at the summit of Mt. Ember, where Moltres is, after the player has caught Moltres and defeated the E4. What flags need to be checked in order to do this? Also is there a list of values for flags somewhere I can use as a reference? (Sorry if this is worded weird. I don't have a complete technical understanding of scripting)

Another one is going to have a legendary appear after a certain number of Pokemon have been registered in the dex, and I have absolutely no idea how to make that work either.

[Edit]: I may end up using the Hoenn Link flag instead if that ends up being easier