Darkle is one of those good words that once you know what it means it just sticks with you. Darkle is the opposite of sparkle. According to Webster’s it has been around at least since 1823 and it is an intransitive verb.
When something becomes cloudy or gloomy it darkles. Another use is to describe a thing that is hidden or concealed in darkness. Then of course you can use darkling and darkled now that you know the meaning.
“It is going to darkle as I go further into the woods.”
“The flower arrangement contained darkled flowers to match the mood.”
“His idea was to darkle and hide the meaning of the mission.”
“As I walked away from the light everything began to darkle.”
Some other sources list the word “Darkel” which is pronounced the same but can be used as a reference to a dark angel.
Depending on what dictionary you use, maddish may or may not appear. When it does appear, it references a condition of being “somewhat mad,” which to us sounds like an excuse to include it.
One of the reasons it does not sound right to us is that it is almost impossible to use alone. If you were saying “somewhat maddish” why not just say “somewhat mad”?
“Jack was maddish at Jill for using all the ink.” just lacks a ring of accuracy.
Not to be outdone, one urban style dictionary actually listed “like maddish.”
We assume this would appear in the sentence, “Jack was like maddish at Jill for spilling all the water.” A real butchering of the language.