Old Teuthish
Old Teuthish is a language spoken in Lõis. It is classified in Lõis as a Germanic language, but relative to our timeline it is a sister of Proto-Germanic. It makes use of several archaisms such as the total absence of Verner's law, and contrastive stress inherited from PIE. It is also innovative in other ways, such as Grassmann's law.
History
Old Teuthish has a lot more historical attestation in Lõis than Proto-Germanic; it's comparable to Old English.
Morphology
Old Teuthish is a pretty standard ancient northern IE language, with a highly inflecting nominal morphology and a somewhat reduced verbal morphology.
The definite article is inas / inā / inan.
There are seven grammatical cases in Old Teuthish: nominative, genitive, accusative, instrumental, dative, locative and vocative. There are also three numbers: singular, dual and plural, with the dual showing up only in pronouns and verbs.
wulχwas, wulχwās wulχwan, wulχwans wulχwassa, wulχwān/wulχwajān/wulχwaān (depending on the dialect) wulχwai, wulχwamas wulχwā, wulχwamis wulχwei, wulχwaisu wulχwe!, wulχwās!