Andreas was born in Germany in 1951.
After first studying at the Fine Arts Academy of Dusseldorf, he moved to Brussels to take courses at the St. Luc Institute and St. Gilles Academy, alongside Eddy Paape. Together they would publish Udolfo in the magazine Tintin.
In 1978, Andreas created a new fantasy series on his own for Tintin, entitled Rork (Le Lombard; Europe Comics 2017).
Following that, he took on a number of new projects both solo (such as Cyrrus and Mil for the magazine Métal hurlant, in 1984) and with various writers and publishers, including Cromwell Stone (Michel Deligne), La caverne du souvenir (Le Lombard, 1985), Coutoo (Delcourt, 1989), and Dérives (Delcourt), a collection of stories written by such authors as Brice Cossu and Yann.
He also wrote two stories to be illustrated by Philippe Berthet (Hiver 1951 and Eté 1960), published together as Mortes saisons in 1985 by Dupuis.
In 1996, Andreas made another big splash with the first book of the fascinating fantasy thriller series Capricorne (Le Lombard), for which he would go on to write 20 volumes.
In 2001, at the Saint-Malo Comics Festival in France, Andreas received the prestigious career achievement award.