Be careful to not split off too many parts at once. This could impair your ability to dodge.
Anything that damages multiple enemies will help you speed up the battle (especially when a larger amount of sections are present on the screen)
Eternal Teratoma is identical to normal Teratoma, but spawns 2 extra Spiders every time it splits.
When the final small Teratoma is destroyed, it spawns a Big Spider.
In biology, a teratoma is a tumor-like growth that contains normal tissue from each of three germ layers (like hair, teeth, or even bones). Like Fistula, these medical facts reference to their appearance (note the bones around Teratoma).