Whomsoever is a 10 letter English word. It's valid Words with friends word worth 22 points.
You can make 342 anagrams from letters in whomsoever (eehmoorsvw).
1400-50; late Middle English, equivalent to whomso whomsoever (early Middle English swā hwām swā; see whom, so1) + ever Examples for whomsoever
Let there be no trifling with disorder, by whomsoever begun.
And there are many Greeks in turn for thee to slay, whomsoever thou canst.
Woe then to whomsoever had transgressed any of the commandments!
These Richard at once proceeded to sell to whomsoever would give the most for them.
Then and there will I hear what this faith is, from him, or from whomsoever they shall appoint.
He left that to whomsoever it might chance to fall—a mangled corpse!
By means of the telephone I could talk with whomsoever I pleased and get the news.
Mrs. Jasher might have let the man in, whomsoever he was, secretly.
And to whomsoever the child gave the apple, that man should marry the king's daughter.
No; whomsoever it was who had repented at the eleventh hour, Mrs. Jasher was not the person.