seven souls gold, sevensouls gold

In the game Crucio Psykeepers with low level monsters with sevensouls gold are best to start, at level 65. By starting with something lower, you gain experience with Crucio-ing which may take time to get use to, and your sta may not be enough for the high mobs such as Glaphan.
Such as Luias who have a spread out spawn is simpler to start off with monsters. When to switch is best? Probably the fastest time to switch is when you can take on a Glaphan without dieing from one critical hit. But this means you will still die from a critical and just a single hit. This is why you have to be careful. If you find yourself dieing too much, go back to Luias or obtain some health or stamina enhancing equipment. This will allow you to train at Glaphans much earlier. So there is no real set level or sta to AoE the mob you want. Just try and experiment and do what is most comfortable to you.
Since V7, new mobs have come out and instead of Glaphans being the highest mob to crucio; the V7 mobs are now crucio-able. However, most of these new mobs have tight spawns and when they're in rage mode, they're quite deadly. So unless you really feel that you are up for such a challenge, to Crucio these mobs at level 80+, you could try it. About aggros and their rage mode just be careful.