basically i used it as soon as i saw a legendary, so i caught Articuno with it lol. Tbh, if i have to be mature, i d probably say that i wouldn't use it anymore now, because despite how frustrating it might be, it's anyway nice the difficulty level of catching a legendary pokémon. i mean, catching a legendary in a normal mode makes u feel like that is actually a legendary pokémon. Master ball kinda kills that feel, but on the other end it also kills the frustration of catching a legendary pokemon. In the last games i feel like it got waaaaay easier. i do remember the most difficult catch was Kyogre in Pokemon Emerald. TRULY HARD. I had like 70 ultra balls and they wouldn't enter. i attempted the catch like 20 times lol. but the satisfaction was amazing when i finally caught it. Yeah, maybe it was a mistake to have deleted the save to replay Emerald, now that i think bout it lol.