They are called "all-powerful" (siddha) because they counteract all defects in their performance, and produce their effect even when the ordinary consecrating ceremonies, as bathing, &c., have been omitted.
Now the peculiar "consecrating ceremonies" (saṃskára) are ten, and they have been thus described in the Śáradá-tilaka—
"There are said to be ten preliminary ceremonies which give to mantras efficacy:
"These mantras are thus made complete; they are thoroughly consecrated.
"The 'begetting,' the 'vivifying,' the 'smiting,' the 'awakening,'
"The 'sprinkling,' the 'purifying,' the 'fattening,'
"The 'satisfying,' the 'illumining,' the 'concealing,'—these are the ten consecrations of mantras.
"The 'begetting' (janana) is the extracting of the mantra from its vowels and consonants.
"The wise man should mutter the several letters of the mantra, each united to Om,
"According to the number of the letters. This they call the 'vivifying' (jívana).