Doomsday-clock for my fantasy planet

I want the surface of my fantasy planet to be made hostile every few thousand years for long enough to make every species go extinct that breeds on land. The easiest explanation seems to be other planets' gravitation, causing every volcano to erupt at the same time when everything is in a certain constellation. Ash will cover the sun and everything freezes for some time.

What size, distance, and constellation would the planets have to be to support such a system?

Hello again. My English isn't that great. That's why I didn't want to make the description too long. Here I go anyway:

With "extinction" I meant that they wouldn't be able to breed on land in this period of time. Many creatures are amphibian, others are hardly considered "living" in the first place and then there are some species that have second DNA which can survive for a long time and then recreate the old species. There are also creatures that live and hunt in underground caves. They come to the surface when the climate changes and "make sure" that nothing stays the same.

A human-like species has to rediscover scripture and can find relics from old civilisations...

posted over 5 years ago

anothernewnamehaha‭

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