I know you said multiple times in the comments that we shouldn't translate names, but Catherine was accepted for Katerina and I wish that just the single most common translation would be accepted... I keep typing Sophie without thinking.
Because you need the accusative case for the object as discussed above. Please read the Tips and notes. You can also read some general introduction, like the salient bits of https://en.wikipedia.org/wiki/Grammatical_case#Indo-European_languages