expression, ichidan verb
to make; to cause to be; to render
Formal, often literary expression used after a noun or taru-adjective to mean 'to make something into that state' or 'to cause to be that way'. It is a causative-like construction derived from たる (classical copula) + しめる (causative auxiliary).
彼のリーダーシップがプロジェクトを成功たらしめた。
His leadership made the project a success.
その言葉が彼を伝
Those words made him a legend.