/iyus''' / इयुस्ऽऽऽ

The hard liG replacement of /jhi is usually **yus युस्, but after short a अ it is /iyus''', formed like this —

hard liG /jhi
→ /jus by jherjus
→ /yAsuT + /jus by yAsuTparasm...
→ yA या + us उस् by other rules
→ (at this point we would ordinarily get **yus युस्. However...)
→ iy इय् + us उस् by atoyeyaH because yA या is after a अ
→ /iyus'''

This /iyus''' then combines with the a अ of the verbbase into eyus एयुस् —

**bhava- भवॱ + hard liG /jhi
→ **bhava- भवॱ + /iyus'''
→ !**bhaveyus भवेयुस् "they would be"