Hexing Squelcher gives your spells ward (pay 2 life) protection and makes it uncounterable itself, which disrupts their plan of using Veil of Summer to protect their combo and forces them to find actual removal instead of countermagic to deal with your pressure. Abrade can destroy key artifact mana sources like their Mox Opal, Chrome Mox, or Lion's Eye Diamond, slowing their explosive turns. Spell Pierce is weak here since Veil of Summer makes their spells uncounterable and also gives them hexproof from blue, so trading it and some filler for proactive disruption is the better plan against their fast combo kill.