A multi-grain selector device includes an outer body having exterior surfaces. The outer body includes a cooling side configured to face a cooling plate of a casting furnace and an opposite mold side configured to face into a mold. The outer body includes an array of multiple grain selector columns each formed from two or more transversely oriented, elongated channels that are fluidly coupled with each other in an end-to-end arrangement oriented along a growth direction that extends from the cooling side of the outer body toward the mold side of the outer body. The selector columns extend to growth openings on the mold side of the outer body. Each of the selector columns is configured to form a single grain column out of the corresponding growth opening that is part of a columnar grained article to be formed in the mold that grows along the growth direction.