The earliest Slovonian dialect did not have a proper alphabet—it was a purely spoken language. Around the 9th century AD, it started to be written in Fuþark (Futhark) runes as a result of Norse influence. Because Slovonia was never successfully Christianized, it continued to use the runic alphabet for several more centuries, instead of adopting the Latin or Cyrillic script like other Slavic-speaking nations. It was only during the reign of Empress Anastasia I in the 19th century, that the present Cyrillic alphabet was introduced. The switch coincided with Slovonia's industrial revolution, part of her desire for modernization.
The new Cyrillic alphabet was modeled after the Russian alphabet in use at the time, prior to the 1917 post-revolution orthographic reform. Hence the use of і (no longer used in modern Russian) instead of и to represent the sound /i/. All letters with unused sounds were eliminated: ы, ъ, and ь. In addition, letters with redundant sounds were also removed: я /ja/, ё /jo/, ю /ju/, and щ /ʃtʃ/. These are now written as ја, јо, ју, and шч respectively. The Slovonian alphabet has 25 letters in total: 5 vowels and 20 consonants. Each letter is always pronounced the same way, so it's very easy to predict what a word sounds like, even if you haven't seen it before.
/e/ if final letter, otherwise /ɛ/