Read the lines from Book 1 of Paradise Lost. Fall'n Cherub, to be weak is miserable Doing or Suffering: but of this be sure, To do aught good never will be our task, But ever to do ill our sole delight, As being the contrary to his high will Whom we resist. Who is meant to be the speaker in these line?

The character that says these words is Satan. He is speaking to the other fallen angels.

Explanation:

Before these lines begin, it is said that Satan is going to say the following words "whereto with speedy words th' Arch-fiend repli'd." The "arch-fiend" is like a super enemy, arch (means superior) fiend (enemy).

Two of the main phrases that prove that Satan is talking are the following:

"To do aught good never will be our task, But ever to do ill our sole delight" = Doing good action will never be our thing, we only find pleasure in doing bad things. "As being the contrary to his high will whom we resist" = since we are the contrary of God, the one we resist.