Partial findings - >
ANAGRAM
WATERFALL
Number's
If there are no specific rules on how many digits each of the three have to write, the numbers were Merlin 12_(127), Mildred-4_6(496), Margana 0583(0583 - Not sure if 0 is allowed as prefix. This is considering that she wrote the numbers between others.) So, the unique numbers on the dashed list were 1,2,4,6,0,5,8,3
SUDOKU
The sudoku grid looks like ->
CRYPTIC CROSSWORD
Perform(ed) any sound(4) - > ABLE -> Perform(ABLE) , Able -> Sound
Lonely crucifix returns stranger(4) - > ROOD-> Crucifix(ROOD) -> DOOR(Returns stranger) Scramble over a thousand(3) -> MIX -> MIX in Roman = 1009(Thanks @Sconibulus)
It sounds like you are an original(3) - > ONE