Once we
>! read the kings' and the land's names backwards, it is clear they are using different bases for the solution.

When King Evif
>! states that the numbers up to 13 shall be displayed, he means eight, as ${13}_5=8_{10}$.  
>! Also, the limit on the sum of digits is ten, as ${20}_5={10}_{10}.$

King Otw:
>! 11101000 for base 2  
>! **1**1101000 = 1  
>! 11**10**1000 = 10  
>! **11**101000 = 11  
>! 1110**100**0 = 100  
>! 11**101**000 = 101  
>! 1**110**1000 = 110  
>! **111**01000 = 111  

King Eerht:
>! 20112210 for base 3  
>! 20**1**12210 = 1  
>! **2**0112210 = 2  
>! 201122**10** = 10  
>! 20**11**2210 = 11  
>! 201**12**210 = 12  
>! **20**112210 = 20  
>! 20112**21**0 = 21  
>! 2011**22**10 = 22  

King Ruof:
>! 12011013 for base 4  
>! **1**2011013 = 1  
>! 1**2**011013 = 2  
>! 1201101**3** = 3  
>! 1201**10**13 = 10  
>! 120**11**013 = 11  
>! **12**011013 = 12  
>! 120110**13** = 13  
>! 1**20**11013 = 20