Pyroblast does have targets here, since Affinity plays blue cards like Utrom Monitor, Thoughtcast, Cryogen Relic, and Baleful Strix. It still stays home because it needs red mana your mana base mostly lacks. Thraben Charm's damage mode (twice your creature count) kills small creatures like Baleful Strix, Glint Hawk, or Refurbished Familiar, and with two creatures out it can even take down Utrom Monitor. Its other modes matter far less in this matchup. Ram Through deals one-way damage equal to your creature's power, so it isn't risky, but it's the most redundant removal slot once Thraben Charm comes in, so trim it. This matchup is a race where their Dispatch can tap down your blockers (and exile them once they control three or more artifacts), so lean on your hexproof creatures and Armadillo Cloak lifegain to out-pace their go-wide artifact swarm.