This card is buffed slightly above a standard equation (factoring power,
toughness, and abilities); hence, the cost of 4 life upon entering. It's very
unusual for a card to come with a cost like this, and this one can't be
turned to the player's advantage (As many costs can), that I know of.
There
may be cards that account for losses of life, and yield a positive
result, but I can't think of anything, off the top of my head. In any case, it is
a strong creature to use, when you are set up to gain plenty of life. The
main point of interest to this card is its creature-type: It would be a
welcome addition to many Spirit decks. Keeping a creature that is this
substantial to a 4-converted mana-cost will certainly help the speed of your
deck, so try compensating with lifelink auras, or the like, for a high-damage
deck that can easily strike the opponent. One of the most useful things you
can do, when developing a fundamental play-strategy, is learn to sacrifice
things (Such as 4 life) to gain an advantage. Played at the right time, in the
right set of conditions, a card like this can be an invaluable asset.