Ambakich language
Aion a.k.a. Ambakich is a Keram language of Papua New Guinea. It is only spoken by adults; children grow up speaking Tok Pisin.

Phonology

 /t/ and /ŋ/ only appear in loanwords.
 /p/ may sometimes be heard as [ɸ].
 /k/ is sometimes pronounced as [q] or [ʔ], usually word-initially.
 /tʃ/ can manifest as [s], or when adjacent to /ɨ/, [t].
 In certain words, the prenasalized consonants are denasalized.
 /s/ is occasionally [ʃ] before /i/.
 /n/ is heard as [ɲ] before /i/, and [ŋ] before /u/.
 Following /o/ and before any other vowel, /w/ is realized as [ŋ].
 Before /a/, /j/ is heard as [ɲ].
 Before the high vowels /i ɨ u/, /j/ is pronounced [dʒ].

 The high vowels /i ɨ u/ do not occur word-initially.
 /e/ is occasionally centralized to [ə].
 /a/ is typically raised to [ə] in open syllables.
 /a/ can also range in realization to [ɛ], [ʌ], and [ɔ].
 /u/ is sometimes unrounded to [ɤ].
 /ɨ/ is often deleted between two consonants.

Additionally, the following diphthongs have been observed: /ai/, /ei/, /oi/, /au/, /ou/.

References

Keram languages
Languages of East Sepik Province
Endangered Papuan languages