"World Shield" is a difficult monster for many decks to defeat and can return to the field repeatedly, while "World Crown" is one of the easiest monsters for the deck to summon and can negate effects
Agate Instigators close, but isnt indestructible, and like Slash, Reptile Rampager are comparable, but more expensive
There really aren't that many things to learn at all
:) So it often comes out, sits as an early deterrent blocker, and mostly gets ignored until the battlefield starts getting a little bigger and then if I need them, constructs start appearing
For example, the Special Energy Card Lucky Energy will allow you to draw a card if your Pokmon is hit with any attack (even if it is knocked out), and draw support is always helpful when playing your game
equip 1 Attraction Trap from your Deck to that target