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The talent mentions that there are other spells, knacks, etc that might let you use Surprise Strike more than once per encounter. Any idea what they are?

I vaguely recall a 1E knack (Double Surprise, maybe?), but if it did exist it hasn't survived.

Thanks in advance.

Conceal Object and Gain Surprise mostly. Memory Blank, maybe.
The rest would be situational, as in: run away, sneak back up.

Mind Wave might do it, too.