when my friend was battling the 4 heads on his ship after he defeated 2 of them the scylla heads spawned the crawlies there were 10 of them lvl 63/64/65 but i did this with 4 crawlies instead of 10.
bloody jordan nightangale lvl 65 my friend dead-eye jose quickly lvl 65
The Scylla heads (I don't quite remember which one/ones) have nautical attacks which can place minions upon your ship during the melee confrontation of the battle via damage tokens. Thusly, if one were to collect said damage tokens, the number of Scylla spawn would be significantly lower than that of a person who did not.
The Scylla heads hit your ships with trap coins. You can lower the amount of Scylla spawn by hitting the tab button and removing them from the deck of your ship before you kill off the second head. Then the battle will start with less spawn on the field. The spawn coins are the yellow ones with the monster faces.