At the imperial Diet of Frankfurt, King Otto IV is officially recognized as the sole monarch; the king punishes the culprits involved in the assassination of his rival, the late King Philip of Swabia, including Henry IV of Andechs, the margrave of Istria (notices from the contemporary narrative source Cronica Sancti Petri Erfordensis moderna).
Mogontinus regiam curiam omnibus principibus Frankenvurt adiendam promulgavit in festo Sancti Martini, in cuius curie celebritate rex Otto confirmatus leges, pacem, edicta Karoli, omnibus principibus sacramentum iurisiurandi prestantibus in id ipsum contradidit. Ibi Ottonem palatinum de Witelsbach, regis Philippi occisorem, sentencialiter vita et rebus proscripsit, quem postea marscalcus de Calentin iuxta fluvium Danubium occidit.
King Otto IV's charter to Duke Ludwig of Bavaria from 1208 - soon to be edited here.
Imperial Diet in Augsburg of 1209 - edited here.
King Otto IV's donation charter to Patriarch Wolfger of Aquileia from 1209 - soon to be edited here.
King Otto IV's re-issue of the donation charter to Patriarch Wolfger of Aquileia from 1210 - edited here.
Although the chronicle does not explicitly mention Margrave Henry IV of Andechs, he was, in fact, stripped of his titles, allods, and fiefs the same way as Count Palatine Otto VIII, and this is confirmed by Otto IV's charter issued to Duke Ludwig of Bavaria just four days following the Diet of Frankfurt (see it edited here), and by Otto IV's two charters issued to Patriarch Wolfger (1209_W5 and 1210_OIV).
For the entire story arc of King Philip's murder and the fate of the Margraviate of Istria during these tumultous times, see the editor's comments in the entry documenting the 1208 regicide.