Back in the days, looking for your roots was so much easier. Twice a year you could just summon your deceased ancestor and ask him about all the nurturing matters.
But speaking seriously: Dziady (in English: Forefathers’ Eve) is a Slavic holiday, dedicated to the spirits. It allowed you (presumably) to contact the other side. After the Christianity entered the Polish territory, Dziady was forbidden, and the practitioners were persecuted. Not fully successfully. Dziady stopped being celebrated across the country, but in many places (preferably distant from the religious centers) was practiced for many years. In Polish literature tradition was preserved thanks to our great poet Adam Mickiewicz and his poetic drama Dziady.
Dziady was celebrated in Poland, but also in Eastern Europe countries, such as Russia, Belarus and Ukraine.
Apart the rituals, Dziady was connected with many other customs. On this day it was common to pay beggars (with food, small objects and even money), so they pray for the souls of deceased ancestors. It was believed that, there is connections between beggars (in Polish also known as Dziady) with souls (which were called by the same name). That’s why they frequently were given the favorite food of dead relatives.
Feasts for the souls were prepared in human houses – so the families could eat together with the souls. During this time, there were special rules. It was forbidden to pour out the water (to prevent wetting the spirits accidentally), to knead cabbage (to avoiding stomping on the ghost) and to bang fist on the table (to not to scare off any spirit). At the time of the feast, ancestors were the only topic of conversations.
Nowadays almost no one practice Dziady in Poland (except, of course, neo-pagans), but there is description of the rituals from the beginning of XX century, from the Latowicki region. People were gathering on November the 2nd. The meeting took place in an old house, then everyone went further – among others, to sacred spot, where back in the days were burial place. The ritual started with the prayer. In the center, there was a fire. Ritual was conducted by two persons: Old Man and the Sorcerer. They were summoning ghosts, which later were fed with fasting food, soaked in milk and honey. It was believed, that souls need to eat and they stay in the Afterlife as long as they are kept in mortal memory. During the celebration, everybody were quiet, and all the faces were covered. Who did otherwise, risked being taken by the ghosts. Ritual was finished before midnight.
These traditions survived in collective consciousness thanks to, mentioned earlier, Mickiewicz. Vision of the poet had strong impact on common picture of folk rituals. Many works of culture were influenced by his poem. For example: in video game Witcher 3: Wild hunt, one of the sidequest was based on Mickiewicz’s Dziady.