[1] Theodore had two elder brothers, Nicholas II and Ladislaus I, who actively participated in the royal military campaigns against the Kingdom of Bohemia in the early 1270s.

[8] It is possible that Theodore supported Archbishop Lodomer, who entered into an alliance with the rebellious Kőszegi family against the immoral and weak-handed Ladislaus IV and agreed to offer the crown to the king's distant relative Andrew the Venetian, who arrived to Hungary in early 1290.

Upon Andrew's arrival, his unidentified opponents tried to bribe Theodore not to hand over the crown jewels to the soon-to-be-king, but the provost refused them.

He was one of the main organizers of the diet, which took place in Óbuda in the first days of September 1290, where Andrew III promised to preserve the rights and privileges of the nobility.

At his own request, one of the articles stated "the old right of the church of Fehérvár to the position of vice-chancellor to be held", thus officially combined the two dignities, confirming the existing customary law.

[12] Thereafter the concluded peace treaty prescribed the destruction of the fortresses that Albert of Austria had seized from the Kőszegis, who, in response, rose up in open rebellion against Andrew in spring 1292, acknowledging Charles Martel of Anjou, as King of Hungary.

The royal troops subdued the rebellion by July, but Ivan Kőszegi captured and imprisoned Andrew during his journey to Slavonia in August.

[12] Theodore and his relatives bought Békásmegyer for 120 silver denari from Ladislaus Balog, lector of Buda chapter.

[17] In February 1298, Theodore was present in Vienna when Elizabeth, Andrew's daughter was betrothed to Wenceslaus, the son of the Bohemian king.

[18] Theodore attended the diet in Pest in the summer of 1298, which authorized Andrew to destroy forts built without permission and ordered the punishment of those who had seized landed property with force.

[12] The Diocese of Győr, which laid in the borderlands between the expansionary Kőszegi and Csák domains, was threatened constantly by looting and plundering raids.

A period of Interregnum and civil war between various claimants to the throne – Charles of Anjou, Wenceslaus of Bohemia, and Otto of Bavaria – followed Andrew's death and lasted for seven years.

[14][20] The Hungarian prelates, led by Stephen, Archbishop of Kalocsa traveled further to the Neapolitan court, while Theodore returned to Hungary.

According to the narration of the Steirische Reimchronik ("Styrian Rhyming Chronicle"), perceiving the intrigue, Theodore Tengerdi and his small accompaniment caught up to the royal escort before crossing the border.