The basics of it:
If you have read the card, you know that Etched Monstrosity takes:
1. five mana to play (any kind)
2. it is a 10/10
3. it comes onto the field with five (5) -1/-1 counters on it (making it a 5/5)
4. for the cost of one of each type of mana (island, swamp, plains, forest, and mountain) the five -1/-1 counters are removed, making it a 10/10 again. You also get to make anyone (even yourself) draw three.
How to use decently:
Personally, i use it in my main deck, which i call my "power beatdown deck". it is great when you have a lot of mana, they do not have many cards left, and you need them to run out of cards. All you do is play Etched Monstrosity, pay the one of each, make them draw three, and hit them without mercy. I like it paired with Karn Liberated, whom i have done a different review on. the other review is called Karn Liberated, wait, can i try that again?
defending yourself against it:
if you have an unsommon, use it after they pay the one of each. that way, they have to start ALL OVER AGAIN.
it is a 10/10; what more needs to be said
it takes ten mana, with at least one of each, to play it. that is hard to do in a real game
i will give this card an 8, only because it has the one of each flaw to it.