Learn Russian: Никто не спорит с этими племенами и вождями. - Nobody argues with these tribes and chiefs.

Племя is one of the special neuter nouns ending in -мя. When declining these nouns in the plural or oblique singular cases, you must first add the suffix -ен- to the root. For the instrumental plural form required by the preposition с (with), you take this expanded stem племен- and add the standard hard plural instrumental ending -ами, resulting in племенами.

Why does вождями end in -ями while племенами ends in -ами?

This difference comes down to hard and soft noun stems. Вождь (chief) is a masculine noun ending in a soft sign (-ь), meaning its stem is soft and requires the soft instrumental plural ending -ями. On the other hand, the expanded stem of племя is племен-, which ends in a hard consonant (н), so it takes the hard ending -ами.

Why are there two negative words (Никто and не) in this sentence?

Russian requires a double negative. Whenever you use a negative pronoun like никто (nobody) or ничто (nothing), the verb itself must also be negated with не. So instead of saying 'Nobody argues', Russian literally says 'Nobody does not argue'.

Since the sentence involves multiple tribes and chiefs, why is the verb спорит singular?