itch.io

Easiest way would probably be to edit cis_intro_part2 and swap out the cc_intro_startermonsterselect / nickname logic; rather than making a monster choice menu and wait for your input, the startermonsterselect script would instead fill your party with the monsters you want:

var amp = amp_get_new_party_id();
amp_generate_monster(amp,monster_id,level)

First get the ID of the first empty slot in the party, then generate a monster there using its species and level, repeat as many times as you want. There's matching get-first-free-slot functions for the boxes and the temporary enemy slots, too.

To go through every monster like this, rather than hardcoding the monster_id you could loop from 0 to MONSTER_MAX.

Also note that if you really want the player to have every monster in the party, you probably want to increase PARTYSIZE_ACTIVE from 6.