Mono Blue Terror is a tempo-permission deck that wins by countering your combo pieces and beating down with cheap threats like Delver of Secrets and Tolarian Terror. Red Elemental Blast is your best card in this matchup, acting as both a counterspell answer and a way to destroy their blue creatures that have resolved. Prismatic Strands comes in to protect your combo turn from Deem Inferior and Counterspell by cycling through your protection suite — post-board they'll have Hydroblast and Annul to answer your combo, so having extra protection is critical. Flaring Pain comes in as a one-of to punch through any Prismatic Strands they might be running to protect their own creatures, and to ensure your damage resolves. Lightning Bolt is largely ineffective since their creatures grow big quickly and are often countered through the permission suite, while Abandon Attachments and one Sandstorm Eidolon are the weakest cards against a non-aggressive blue deck.