Let me start by saying I chose the slivers who's abilities were global. I decided it would pay off in the long run, by making it easier for them to get smarter. as for the specific reasoning for each card in my "Counter Sliver deck". I think its best to do this by color, lets start with the white cards:
The plated slivers are obviously really cheap cards that have a stacking global ability. The essence sliver well thats to gain life mid to end game (if i draw it, its expensive casting cost is why there is only one of them.) And the pacifism is just there to stall my opponent, and maybe play a lilt head game wit him too.
Now for the deck's green cards: The muscle slivers, these guys explain theme shelves. the Brood Sliver well he's got a great ability that works well with others. Again only one of these bad boys made the cut because of the high casting cost. Tribal unity, well hey who doesn't like a little +X/+X.
Blue is the core of my strategy, being the largest portion of my deck. The shifting slivers provide unblockability mid to end-game, helping my creatures get damage across.It's high cost made me reluctant to use him, but in the end he was a needed member of the team. Another card which has no need for explanation is the four Winged Slivers, but I will--they provide evasiveness early on in the game, helping my brood live to reach mid-game. Now u may be asking why the one Mistform Sliver? The answer is its another cheap body.(while its ability could help sway A game against another tribal deck, like zombies). Miscalculation a cheap counter spell--that cycles is a plus (helps get the card you need). Mana Leak while costing the same as a miscalculation costs an additional 1 for opponents to counter. Counter spell, This my friend is the ultimate denial card, more expensive that the previous two rejection type spells, but more powerful. Propaganda these things really help discourage attacking, with their stacking abilities.
Now the multi-colored lot provide powerful abilities and help tie the decks colors together giving it a unified theme. The two Victual Slivers provide the needed life early to mid game, while not as nice as its cousin the essence sliver, he is faster making him viable.Crystalline Slivers by far the corner stone of my deck, giving my creatures untargetability.
Metallic Sliver the only artifacts in my deck provide the cheapest means of dropping a creature quickly,make the numbers of slivers grow that much more faster.
)