May mystically describe this method (e.g., Liber HHH, Section 3). But the course of history will determine the sense of the passage.
"Lurk! Withdraw! Upon them!" describes the three parts of a certain magical gesture indicative of a formula which has proven very powerful in practical work.
(The events beginning in An XVII Sol in Libra, when I write these words, and ending I do not yet know when, will form a luminous comment on the passage. There is an alternative, taking the beginning as An X sol in Libra, and implying larger periods).