"...Just watch me"
Not just Giana but the others are also shocked from hearing what Rex just said.
The Vampire stronghold is fortified heavily by the Werewolves, Undead, and Vampires. High-ranking Supernaturals are crawling there fending off the constant effort from the Cessation Knight, it's a big declaration even with Rex's current power.
Despite the stronghold being left to be built, humanity did that not without a reason.
Just like humans, Supernaturals also have teleportation formation that can summon reinforcement on a whim. If they wanted to take down the strongholds then they need to hit hard and fast.
But even if they did do that, they will definitely suffer many casualties.