インスタント
クリーチャー最大2体を対象とし、それらをタップする。
調査を行う。(「

, このアーティファクトを生け贄に捧げる:カードを1枚引く。」を持つ無色の手掛かり・アーティファクト・トークンを1つ戦場に出す。)
You can cast Expose Evil with no targets if you only want to investigate.
If Expose Evil has at least one target and all of those targets become illegal, the spell doesn't resolve and you won't investigate.
If an effect refers to a Clue, it means any Clue artifact, not just a Clue artifact token. For example, you can sacrifice Wrench to pay for Alquist Proft, Master Sleuth's activated ability.
You can't sacrifice a Clue to pay multiple costs. For example, you can't sacrifice a Clue token to activate its own ability and also to activate Alquist Proft, Master Sleuth's ability.
Clue is an artifact type. Even though it appears on some cards with other permanent types, it's never a creature type, a land type, or anything but an artifact type.