Astrid Thomas grew up in Frankfurt and had an early interest in the occult. Her zeal in studying hidden forces earned her the interest of Tremere Primogen Patricia von Bernstein, who recommended her to her clan mate Nathan Mendelson. Mendelson took Astrid as his ghoul and the two traveled to Vienna. After six years, she received the Embrace from Etrius himself, who had took a liking into the young woman.
When Napoleon's forces occupated the city in 1805, thanks to the aid of the Toreador representative Maria y Aragon, Astrid Thomas was vital in preserving numerous Chantries from the French and the following Toreador, mainly through the use of mortal agents. During the Congress of Vienna, Thomas' influence managed to drive most, if not all, Toreador from Vienna. In the following years, however, her main work was diplomacy with the Clan of the Rose, allowing them re-entrance and a say in the various reconstruction projects of the city.
In the wake of growing conflicts with german Princes, first among them the Ventrue Prince of Berlin, Gustav Breidenstein, Thomas' talent for diplomacy meant that she was often sendt on missions abroad, seeking dialogue with the prince. During one of these travels, agents of Breidenstein captured her near Frankfurt, using her as pressure against Etrius to end the Austro-Prussian War of 1866. Etrius sendt her former domitor Mendelson to free her, who managed the feat in 1879 and smuggled her back to Vienna.
In the following years, Astrid Thomas came into conflict with several influential members of the rest of her Clan who sympathized with the German occupation and annexation of Austria in 1938. When Etrius managed a truce with Breidenstein in 1939 to protect Vienna against roving bands of socialist Anarchs, their relationship took a heavy blow that only a renewed Blood Bond to preserve the unity of Clan Tremere in their main city could mend.