This is a sentence from a character bio, but for whatever reason -maybe the author's quirky- they've written it in a really verbose way in what seems to be classical Japanese. I get the general gist of most of it but this one phrase is getting me kind stuck.
[She] finds in [him] an attribute that is the next era's foundation? A disposition of those who will be founders of the next era? I feel like I've gotten the general idea (I think?) but I just don't know what would be the right way to put it into words. This is the first time I've come across たる and it's...pretty confusing.
If it helps, I'm pretty sure the sentence is referring to a scene when the character who's bio is in question thought "he could become a good leader, because being able to change peoples hearts is like a requirement (the word used was 必要条件【ひつようじょうけん】 which I feel ties into the use of たる since たる is apparently used to refer to requirements?) of leaders."