"The master admires a powerful cats" is correct over "The master admires powerful cats"? Confused.
"a powerful cats" is not correct English. You can use "the powerful cats".
The answer that I got wrong was "The master admires powerful cats." Duolingo indicated that the correct answer was "The master admires a powerful cats" which is definitely not correct english - hence my confusion.
The high valyrian sentence seems equally incorrect. Kostōbe is in singular and kēla is in plural, or am I missing something?
You're correct. The High Valyrian is wrong. It should be kostōbī.