Triggered abilities fire automatically when conditions are met
All walls have defender, but wall refers to a creature type, not the keyword
"Lathril's Chant," a favorite tale among the elves, tells of Lathril's birth, deeds, and later ascent to godhood after her battle with a mysterious Cosmos Monster called Eidermaw
There are plenty of ways to make it happen, however, whether its just playing creatures with Flash or bringing in creatures via Ninjutsu abilities
So, each Doctor gets a special TARDIS frame version you can find in the sets Collector Boosters Magic cards are rectangles, and the TARDIS is too so why not put them together
I can see this being pretty solid in decks that ramp out really fast though, since even casting this on 3-4 mana lets you look at a solid chunk of your deck