Card Kingdom: Channel Fireball: Star City Games: ABUGames: Theres a lot to unpack here, and Im not going to dive into every single characteristic by website
They require you to go five turns without taking damage (or proliferate their filibuster counters), but there are many ways in blue and white that can keep you clear from danger, like Magus of the Moat, fogs, and Ghostly Prison effects
Plus, you get information about whats in your opponents hand for your troubles
It is a crucial card for handling problematic permanents without risks, allowing for a safer strategy
In the case of Madame Vastra and Jenny Flint, Vastra provides the damage while Jenny boosts Vastras power
Destroying creatures, giving them flying, regeneration, pumping them up by +1/+1 for each activation, or protecting them by placing them on top of your library