The Demon King challenged God to a baseball match.
Literal
Demon-King [subject-が] God [target-に] baseball [with-で] match [object-を] challenged.
勝負を挑む ('to challenge to a match') — 挑む (いどむ, 'to challenge/confront') takes に for the opponent and を for the challenge itself. で marks baseball as the means of the contest. A humorous, absurd scenario.