Started from the Bottom now we're ERE

Needs Roads to Power. Master Todor (1178) is the intended start: a landless adventurer inside imperial borders with money and prestige - though NB with Khans of the Steppe enabled the wiki recommends Robert Phrangopoulos (1066, Wandering Exiles) instead, since the Mongols make a mess of 1178. Buy the estate via Procure Estate with a duchy-plus patron in the Empire: 1,000 gold plus a weak hook, high prestige or high piety (sway the patron first if needed; you'll lose your adventurer special troops on landing). Then the imperial climb: stockpile influence, request a governorship, Influence Candidacy for your line, boundary disputes for land - or go Co-Emperor and Depose for the bloodless version, which is Your Eternal Reward adjacent. Emperor doesn't need to be the same character; the line succeeding is enough.