Because just one language isn't enough.
Old Thuthic is a Satem language of the IE stock that is attested from the 900s AD in what is now Karelia. Its verbal system is Greco-Aryan in origin, but under influence from the surrounding languages has become much more transparent.
Since I'm starting to get tired, I'm just going to post some sound correspondences. Note that aspirates lengthen a preceding vowel.
*p -> f
*b -> p
*bʰ -> :p
*t -> θ
*d -> t
*dʰ -> :t
*ḱ -> š
*ǵ -> y
*ǵʰ -> :y
*k(ʷ) -> h
*g(ʷ) -> k
*g(ʷ)ʰ -> :k
*m -> m (but -> n word finally)
*n -> n
*s -> s
*w -> w (but -> Ø / C_)
*l -> r
*r -> r
*y -> Ø (but maintained word-medially)
The vowels develop as follows:
*o ō -> a ā
*Ṛ -> eR
Then:
*ĕ -> ɨ <ä>
*ĭ ŭ -> e o
*ā -> o
*ē -> e
Some numbers: enas, to, θres, häθor, fehä, säš, säftän, ašto, näwän, täšän, wešäθ, šäθan.
And some animals: äšwas, awäs, yos, mus, aršas, wärfo, wärhas, kos, sus, šo (genitive šonäs). A cookie to anyone who can decipher all of these before I wake up tomorrow.