by Herman Chau and Rahul Sridhar, with crosswords by Adam Hesterberg (Latin), Dan Gulotta (French), and Jenny Nitishinskaya, Manya Tyutyunik, and Tanya Khovanova (Russian)
Each crossword grid can be solved in two ways corresponding to the two sets of clues. Each solve is in a different language, hinted at by clues which sound awkward for an English crossword, but would make sense as conjugations in a different language (e.g. "You murder" or "We chowed down").
The languages used can be determined by looking at the set of clues for the other solve in each pair. For example, in the Spanish and French pair, the Spanish crossword clues contain the word "French" and vice versa.
Overlaying the two solves for a crossword grid yields three or four overlapping letters. Reading these letters from left to right, top to bottom in each crossword in order gives the answer ECUMENICAL.
The solutions to each pair of crosswords are in the pdfs below:French-Spanish