While agreeing with SA, I might add that Oracle of course works with cyrillic characters, if set up properly.
settings on the server AND the client that they support the language you use.
Note that the Server and the clients need to have the same setting and that you can't really change the setting on the server after installation while the
settings affects the tables on file level.
setting is of course to use one of the UNICODE settings and not some national codepage, that would effectively turn varchar2 into nvarchar2.