Jace's Scrutiny

The math on the front is the whole pitch: a -4/-0 swing turns most attackers into a non-threat for a turn without killing anything, the soft answer blue reaches for when it cannot afford to trade resources outright. It functions as a single-target Fog, neutralizing one creature's combat damage rather than the whole board, and it leaves the blocked attacker on the table for next turn. The second clause is where the design earns its card slot: Investigate converts a one-shot defensive spell into a half-card of stored value, smoothing the obvious downside of any combat trick (that you have spent a card to win a single exchange). You do not draw immediately; you bank the Clue and cash it later, paying two mana and sacrificing the token to draw a single card when your mana is loose enough to afford it. That deferred structure is the quiet honesty of the thing: the effect is cheap and the replacement is real, but the replacement costs additional mana and consumes the token, so it never reads as free. As tempo math it is unremarkable; as an illustration of how Investigate was tuned to make narrow effects worth including at all, it is a clean example of the mechanic doing its intended job, stapling a delayed card draw onto an effect that would otherwise vanish the moment it resolved.