E, I, I, E, I, I, O, H, W, ?

The required missing term is N.

EXPLANATION:

The visible terms in the given sequence correspond to the second letter of each word when the numbers 10 (TEN), 9(NINE), 8(EIGHT), 7(SEVEN), .......2( TWO) are considered.

The next number is 1, which is "ONE" when spelled out and the second letter of "ONE" is N.

Thus, the required missing term is N.