The affix tasi comes after that Ablative -5th case which is ordained owing to the union with the karmapravacanīya word prati,
This Ablative case is ordained by Sutra 2.3.11. Thus प्रद्युम्नः वासुदेवतः प्रति, अभिमन्युरर्जुनतः प्रति ॥ The anuvritti of वा \optionally\ runs here also: thus it is an optional rule; we have the regular forms वासुदेवात् &c, also.
Vart:- The affix तसि comes after the words आदि &c: as, आदितः, मध्यतः, पार्श्वतः, पृष्ठतः &c. This is an akritigana, no complete list being given.,