I highly recommend that you got out and buy a couple of decks (any of the Duel Decks are great starting points) and set about understanding it
As a largely casual format, Commander has also influenced the rise of proxies for casual play
Again, like the Elder, you generally wind up playing planeswalkers over Den Protector due to their overall cost being in the same sort of range
Those first cards are useful, but to properly challenge the islands eight elemental Club Masters, Pokmon Trading Card Game requires you to cultivate more powerful decks that play to different types of advantages and feature cards you pull from booster packs won by dueling NPCs
An Oubliette is a prison, so this ability lined up pretty nicely
If the enchantment has no cost, it is constantly in effect