Some trainer cards allow you to draw more cards from your deck, others allow you to search your deck for specific cards, and still, others let you do things like heal your damaged Pokmon or put new Pokmon into play
Some notable facts regarding Rooms: If a Room enters the battlefield without being cast both doors will start locked and neither ability will be active
Electrode's Chain Lightning attack is more effective when the opponent has more Benched Pokmon, at least of the same elemental type as their Active
The light transparency check is helpful In authenticity checks for Pokmon cards, the method of looking through the card against a bright light is frequently used
They're not even an insect-person like Xira Arien above
Even if you steer clear of combos, extra combats seem like the way to go to squeeze as much mana from Preston as possible, not to mention all the damage you get from suiting up creatures with cards like All That Glitters and Ellivere of the Wild Court