As mentioned earlier, the best way is by casting your spells at instant speed, putting your creatures onto the battlefield without casting them, and stopping your opponents from casting multiple spells each turn
But if youre going all-in on a keyword ability or ability word, landfall is one of the best choices
On the other hand, Giratina EX uses Red to OHKO non-Cape versions of most Pokmon
Chamber can search for any of your Dragonmaid S/T, it's usually what you are going to search with Maid's Downtime , you can run 2 copies of Chamber because of the consistency of the skill, but I recommend playing 3 to search for other potential combo pieces with your skill
That being said, since there are much more affordable variants of these cards available, their prices hardly follow the norm