Blood Senate (concept)
A 'Blood Senate' is both the name for the accepted succession system of the Aversarinas Aautokrata and also for the actual gathering of nobility to perform it.
First began in 243 IS after Aautokratir Akalionixos declared that whichever one of his sons could prove themselves the strongest Magi may succeed him, he was soon after murdered by his daughter Maklea in an impromptu duel, who was shortly after declared aautokratia and spent the rest of her reign largely hunting down her brothers. This was its origin however, and a thousand years of formalization and correction to attempt to prevent massive civil wars nearly every generation have led to its modern iteration.
In the modern world, a Blood Senate is declared just after the time of mourning for the former Aautokratir. The high nobility of the realm choose an agreed upon location and each noble family puts forward one candidate to compete, though other members are allowed to volunteer as well (though this is taboo) and non-nobles are also allowed to join, though this is also taboo.
During a Blood Senate, the assorted candidates compete in a bracketed tournament to find who is the most powerful Magi via duels to the death, with no mercy allowed at risk of disqualification. The last man (or woman) standing wins.
Only one Blood Senate has been won without Magic, by the Aversarian mercenary Nothyx, who used Anti-Magic skills learned from the Marchers to put down his competitors with nothing besides his sword.