pilica12
Buriallusion: Phantomic Killer in Night Mist
Short answer... it depends. The lag that worked for Blacephalon is unlikely to work for other every other legendary. For example, my Stakataka's lag value was ~400, my current RNG attempt at Celesteela is sticking around ~500, wormhole Yveltal and Cresselia were around ~-300 and Zapdos was ~-600. Of course, you are free to just use the lag you currently have and then adjust it for the legendary you are trying to RNG. There is no difference in this, compared to just starting again at 0. You will have to undertake the lag "adjustment" process every time, since the lag varies from legend to legend, and is also dependent on your console (i.e. my lag may not match yours).~snip
As for Magearna, let me just observe that it is one absolute pain to RNG (even with the assistance of PokeCalc). Usually it is safer to RNG Magearna with 6 NPCs (that is the default setting on the RNG Tool); however, to do this, you must make sure that the "walking NPC" is not on the screen during the RNG process or everything gets messed up. From my experience, you should ensure that the NPC is far away so it doesn't affect the frame advancements by being too close.
When you select the legendary you are RNG'ing in the Tool, it gives you a preset delay; just use that and adjust the lag as outlined before. And as for checking frames, if you are doing this manually without the assistance of PokeCalc, there is no way to check the frame you hit without catching it, checking its nature/IVs and then using the Tool to find the frame you actually hit. Good advice would be to simply use the Master Ball and check the nature/IVs of your catch during the first ~5-10 trials to get your lag right. After that you can catch "normally" if you want matching Poke Balls. Of course, this is a rather time-consuming process and is certainly not easy. For reference, Zapdos took me about 20 hours of trying! The only real tip I can give for catching is somewhat self-explanatory: lead with a relatively low-level Syncher of your choice, use a Roto-Catch on Turn 1 and let the Syncher die (this prevents it from gaining Exp, saving you time). Switch to a Level 100 Sleep 'mon with False Swipe (I personally use Breloom and I can give you one to use if you want), knock the legendary to 1 HP, Sleep it, and then chuck Balls until it is caught. Obviously only worry about this after you have gotten to a consistent lag. Until then just let your Syncher die, switch, Master Ball, check, figure out your frame then soft-reset and try again.
If you "accidentally" hit your frame during the calibration process, thereby using up your one Master Ball, if you're happy with your catch, feel free to ask as I am happy to provide extra Master Balls for your use.