The Piaszczyński surname is among the co-heralds of the Ostoja coat of arms.
Coat of arms legend:
In 1069, Bolesław the Brave granted the Ostoja coat of arms to a certain knight.
This knight captured the advance guard of pagans, and one of the prisoners promised him,
swearing on the sun that in exchange for freedom and the coat of arms he would help destroy the rest of the enemies.
He returned to his people, reassured them that there were no Poles in the area and led the pagan troops one by one
into the ambush set by Ostoja. When reinforcements arrived, Ostoja attacked the unprotected enemies in the first place and for a week from quarter to quarter the Poles cut down the pagans.
As a reward, Ostoja received a coat of arms with two months (crescents) and a battered sword. Marek Derwich, Marek Cetwiński, Coats of Arms, Legends, Old Myths, p. 73
Ostoja. When two moons defected ceruleans dorsis contra se rendentes,
cruce etiam cerulea illas intersecante, in campo rubeo defert.
Jan Długosz, Insignia ..., no. 87, pp. 61-62
Ostoja.
Which two incomplete wax [gold] moons arranged with their backs opposite each other,
and with a wax [gold] cross those [moons], in a red field represents.
Translation Danuta Szopa.
There are to be two yellow incomplete moons, turned sideways to each other,
each with one corner up, the other down,
between them a white sword, chipped, hilt up, tip down,
in a red field, on the helmet five ostrich feathers.
Kasper Niesiecki, Herbarz, vol. VII, p. 170
Taken from the website: www.herby.com.pl