how do leblank

leblink mains tell me your secret rituals. how does she work, what do I do. they must've done something right with the whole mystic trickster because I can't tell what the hell she does even after all this time playing her and reading the kit. what's her ult. how am I sometimes able to double and triple cast it in fights. how do I actually use it to pop her passive rather than just spamming r e for some more roots. why did a leblanc I saw a while ago just pop out of literal nowhere and one shot the adc while I was off warding and there was vision for the entire jungle around and she was under tower and then she was gone I don't even know what happened to this day. why don't people recommend leveling e earlier since it does way more damage and syncs up with her passive perfectly and why is she more complex than shaco now?