From the FAQ (http://bbs.evony.com/showpost.php?p=490730&postcount=3) we know what level title you need to persuade heroes:
Hero Level Title Needed
01 - 09 = Civilian
10 - 19 = Knight
20 - 29 = Baronet
30 - 39 = Baron
40 - 49 = Viscount
50 - 59 = Earl
60 - 69 = Marquis
70 - 79 = Duke
80 - 89 = Furstin
90+ = Prinzessin
From gathering data over the last few days we now have the formula for how many and what type of medals are required to persuade a hero for each hero level:
All levels from 131 and up require nation medals, and they increase by 1 medal per 10 levels. The formula then becomes ((HeroLevelRoundUpNearest10) - 50 (ie. the base levels)) /10 (levels per increment).
Hero Level 278 requires = (280-50)/10=23 Nation Medals
Hero Level 200 requires = (200-50)/10=15 Nation medals
Hero Level 183 requires = (190-50)/10=14 Nation Medals
Cross to Justice medals always require the fixed number of medals listed for persuasion.
The amount of gold required is always 1000 gold per level.
**We do have some data that do not fit the formula. The few cases have been with higher level heroes, where the amount of medals vary by a few medals in each direction. We also have a case of the same hero being passed from person A ? B ? C and requiring different (lower) amount of medals each time. As such, there seems to be a factor not yet discovered. In the case of the same hero being passed around it may have been due to prestige differences, but we suspect the hidden factor may actually be the number of times a hero has been persuaded. It could of course also just be reporting errors.
I?m releasing the raw data below, and I would like people to contribute more data to either confirm or show otherwise so we can get accurate predictions for all hero levels. Screenshots are not necessary, but please make sure you indicate attributes with/without boosters. Please also indicate which server the stats are from, just in case there are different requirements across the servers. Most of this data is from server 4. Thank you to those who have contributed data.