The Mondragon family, the manor of the town of this name in Vizcaya, province of Guipúzcoa is very illustrious and ancient.
The arms of this illustrious house of Mondragon, increased as it is expressed in the actual ceded already mentioned, are: split shield; the 1st. of gold and band of gules, swallowed of dragons of sinople; cut of silver and two castles of stonecut joined by an arch of the same that passes from the battlements of one to the ones of the other in the form of bridge; below it and between the two castles, a tree and a wolf attached to the trunk with a golden chain; the 2nd, cut in two by a gules band loaded with a gilded gusset overloaded with a grenade; the 1st. of silver and an arm that wields a flag of gules of two ends, loaded with a waning of silver; the 2nd. of gold and three heads of Moor.
Don Felipe, by the grace of God, King of Castile, Leon, Aragon, Granada, Toledo, Valencia, Mallorca, Seville, Sardinia, Cordoba, Corsica, Murcia, Agarbes, of Algeciras, of Gibraltar, of the islands of Canaria, of the Indies and Islands and Tierra Firme delmar Ocean, count of Flanders, Tyrol, etc. = Since part of Melchor de Mondragon, a neighbor of the city of Ronda, son of Garci-Benitez de Jerez, also neighbor of her, we have been told that for the month of January of this present year of 569, having had notice the said city that the Moriscos of the place of Istan, which is of jurisdiction of Marbella, had risen, our corregidor came out of that city with up to two thousand men to follow them ... where you were and up to six armed with their weapons on horseback, the people of the said city arrived at the foot of the mountain where the said Moors were raised, and seeing that they had gone from there to another mountain, you were with the said six men following them. saw down, where they went, to the Green River; and then another day, you went up to the Picacho mountain range, which they say about Marbella, where the Moorish lands had risen, and in the middle of it you ran into a group of them up to twenty, and some with crossbows and others with other arms, and the one of them brought in silk cendal, which he confessed to be a flag of the said uprising Moors; and you, the said Melchior of Mondragon, ordered the said six men, who put themselves in order to fight with them, as they did, and attacked them by advancing you, and disarmed them and captured all three, one of them the lieutenant, to which you removed the said flag, with which to the three trugistes captives to the said city; supplicating us, that, having regard to the aforesaid, and because of the remembrance of it, to your descendants, we were to do you the favor and honor of giving you and increase you on the arms that you have of your past, a shield also of arms, where in a field of silver have an arm which in your hand has a two-pointed colored flag with a white blade; and in the other half three heads of Moors in a field of gold, with a band of blood, with a grenade in a field of gold, which strips away the metals, or as our mercy.
We, in accordance with the aforementioned, that because it cost what is referred by information that before some of our council presented, taken by the corregidor of said city, by the present of our own motu and certain science and absolute real power, that in this part we want to use and use, as king and natural lord, not superior recognizer in the temporal, we make you merced and we want and we command that of the arms of your past you can increase and to have and to bring by your known weapons, the above declared and placed in your shield as it is contained here.
The coat of arms is figured.
Which we give by your known weapons that they keep you and fulfill and enforce and keep this our letter, to you and your sons and daughters and descendants of them and of them and of each of them of this merced, that ansi we make you of the above-mentioned weapons ... In testimony of which we gave our letter of privilege, signed by our royal hand and sealed with our seal and endorsed by our undersigned secretary, of which we command that the reason Antonio de Arriola, our servant.
Source: http://heraldicablog.com/2010/09/23/mondragon-escudo-heraldico/