What To Do:
Your goal is to overwhelm everyone and end the game as soon as possible. This is done via massive unblockable slivers. You can potentially have a nuts turn and take everyone out at once or just pick each player off one by one and recover in between. How do we get there? If you're going to play The First Sliver, you might as well cascade like there's no tomorrow. Look for windows of opportunities to kill everyone. Don't go off too early and don't go off too late.
This deck is good in a multiplayer game and good against 1 v 1 aggro, but less good against 1 v 1 control.
The deck's strength is its commander. The deck's weakness, however, is also its commander. We can play without The First Sliver, however the commander is what makes this deck unique and powerful. Playing without it slows the deck down drastically. Protect your commander at all costs. Though, if it does die, you do get to cascade again by recasting it.
Note: it's advisable to kill the players who have board wipes first, especially those with Cyclonic Rift or Evacuation because they're instant speed (we lose a lot of tempo and hasty slivers won't save us), regeneration and indestructible don't work.
It's important that you make a strong board, both power-wise and resiliency-wise. The First Sliver is already a good card for this; with so much cascading, you'll end up seeing a large amount of the deck, including all the slivers you need. To increase consistency we have Sliver Overlord, Hollowhead Sliver and Homing Sliver as well as a copy of Bring to Light and Congregation at Dawn. CONSISTENCY IS KEY; the deck needs its protection pieces in case of blow-outs. I cannot stress this enough; the deck needs to consistency do what it's designed to do and weakness comes from only being able to do it SOMETIMES. For utility we have Shapesharer and Dregscape Sliver.
A go-to search is a sliver that gives your team haste (Cloudshredder Sliver, Heart Sliver or Blur Sliver) and a sliver that gives your team mana (Manaweft Sliver or Gemhide Sliver). If you have The First Sliver on board, you'll be able to cast a sliver, cascade, get more hasty mana from your cascades, rinse and repeat. It's also a good idea to fetch for a Crystalline Sliver or any slivers that protect individual slivers from kill spells.
Mulligan:
You want 3-5 lands in your opening hand. Any more than 5 is bad and any less than 3 is equally bad. You also need to make sure your lands hit all the colours (obviously). Best is 4 lands with a piece of ramp and some cheap slivers. When considering mulligans, the land count is the focus.
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5 lands is manageable as long as the other 2 cards are playable slivers or enablers (or just great cards for when The First Sliver is on board): it's not critical you play anything before your commander comes down. Like Maelstrom Wanderer the deck can be slow on early turns, though is explosive on later turns. However, any more than 5 lands is bad because you don't want to risk sitting there for 5 turns doing nothing.
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3 lands is keepable as long as you have some decent, cheap plays or ramp. 3 lands is the minimum, as if you have 2 lands all the non-sliver ramp you might draw would be offline (the cheapest being at a 3 cost).
If you open with a suspend card it's not the end of the world! In fact, it's great. Cascading into a suspect card may guarantee a pseudo-power card on the spot, but playing them on turn one guarantees the effect on turn 4 or 5 anyway. Sure, you're down a card, but it could be worse. The suspend cards on resolving on turn 4 or 5 might just give you the boost you need to go into The First Sliver. However, please do note that the late game potency of your deck will be reduced.
The Plan:
Turn 1-4/5 get up to 5 mana while playing some cheap slivers. Attack some people while you're at it. Turn 4/5 play your commander. From turn 6 onward, go nuts. In these later turns it might even just be a good option to hold back from attacks and just cascade until you get all your protection and evasion so you can guarantee some kills without risking your board. If you hold back and just cascade you'll also be able to get the full effects of all the 0 cmc pseudo-power cards. If your meta has a lot destruction it might be advisable to play some protection before you cast The First Sliver. You can either wait or search. Alternatively, you can just ignore any threat of destruction and cast The First Sliver to cascade into the protection you need. In the early game the deck is carried by the pseudo-power, while in the late game, its carried by its resiliency, recovery tactics and the advantage you get from high cmc non-sliver spells.
Late Game:
If you haven't killed your opponents yet, it gets a bit rough from here. However, the deck's resiliency and recovery is what will get you ahead in the grind. The deck is fast but can also benefit from being played slow. In fact some of the best plays comes from waiting for the right moment to strike. Quick Sliver shines in the late game where you can get some surprise kills by amassing giant boards at the end of your opponent's turn out of nowhere. Hasty slivers can also work towards surprise kills. Hold these cards in your hand without revealing too much.
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In a late game without wrath effects, ensure your evasion pieces are protected. This is key in finishing your opponents off. If you can protect these pieces of evasion, just cascade a few times for a big board and swing away. Kill any body capable of killing you quickly first. The damage ceiling of this deck is high and can kill as quick as some of the quickest decks, thanks to Sliver Legion, Magma Sliver, Bonescythe Sliver, Fury Sliver, Mirror Entity, Shared Animosity and Coat of Arms. Combining this with Kindred Dominance can be savage. Constricting Sliver is great here and can remove an opponents whole board within a few cascades, letting you attack relentlessly without fearing backlash. Equilibrium is also good as removal. This can potentially remove multiple creatures or even whole boards with a few good cascades. Better than Harsh Mercy as if you cascade into it you don't necessarily have to use its ability immediately. In a battle of attrition Ward Sliver, Thorncaster Sliver or Brood Sliver is what you need. Ward Sliver is also good in these cases doubling as protection from removal and evasion. Synapse Sliver is great for replenishing the hand and gaining long-term advantage. It's also 5 mana-cost and thus great for cascading. To prevent decks that can one-turn-kill or voltron decks, Sentinel Sliver is very useful, as you'll have blockers after you swing; so is Crib Swap. Against prison decks, you'll need to rely on your disruptive cards such as Necrotic Sliver.
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In a late game WITH wrath effects, it's much harder. You'll be excessively reliant on the slivers that protect your board. If you can stabilise with these, you'll be fine. If not, you'll be in a bit of a pickle. Strategically it's good to team up with other aggro players to kill whoever's got the wipes (being in the best of all your interests). If you do this, you can then make short work of the players without wipes. If this isn't possible or the remaining player(s) all have wipes, you can rely on Lavabelly Sliver and Purphoros, God of the Forge as well as attempting one turn kills with hasty slivers. Combine this with cascading and graveyard return effects for the best results. This alone can overwhelm opponents. Sometimes it might be better to sit-back and do nothing until you can set-up all your resources to achieve this. Patriarch's Bidding in these circumstances can be brutal for most decks without many creatures. Mesmeric Sliver is useful in the late game if you can do multiple fate-seals against your opponents to remove their wipes. I personally don't play Mindlash Sliver though this is also a damaging card against control decks. Against control decks that are also combo decks, just get as much dps as possible. Apart from that, we can't really interact with their combo. Politically, it should be fine as they will likely just end up as the archenemy anyway.
Blow Outs and Recovery:
Sometimes other players will feel an urge to blow up your board. To counteract that we have Sliver Hivelord, Frenetic Sliver, Crypt Sliver and Hibernation Sliver. Though, even when you don't have these cards, the deck can recover very fast. This can be attributed to the boost you get from the 'power nine cards' as well as the enchantments that draw you cards for each creature you cast/ each creature that enters the battlefield. With a hand full of goodies, you'll be back to full power in no time. Do not overextend your board; that means keep some high cmc slivers in hand as a recovery option and don't always activate your hide-away lands if you don't need to. If worse comes to worse, we also have a copy of Patriarch's Bidding to resurrect everything. We also have other resurrection effects, including Volrath's Stronghold and Graveshifter or even Dregscape Sliver. Phyrexian Reclamation is currently being tested as a recovery option as well.
The worst situations are ones involving non-generic wrath effects such as Cyclonic Rift or Evacuation. As stated above, this is because they're instant speed (we lose a lot of tempo and hasty slivers won't save us), regeneration and indestructible don't work. The former is particularly bad as it bounces your expensive enchantments/artifacts. However, most of the time you can just replay your hand. Regeneration and indestructible also don't work in the case of exiling wraths, such as Winds of Abandon and Merciless Eviction. In these cases it's very hard to recover. What matters is what you do to prepare for these. Do not over-extend your board by wasting your hand and ensure you have the slivers that will save the team, such as Frenetic Sliver and Hibernation Sliver.
Edit (27/06/19): Strategically, I would actually like to correct myself and suggest that in a wrath heavy meta, it is CRUCIAL to wait for your protection pieces before going off with The First Sliver, UNLESS you are certain you can kill people then and there. Sometimes you'll find it very difficult to recover if you over extend. Use your acceleration and dig cards to find your pieces while applying light pressure by summoning a few expendable slivers.
Note: Holding a Quick Sliver and a sliver with recovery or protection is really powerful as it allows you to respond at instant speed to your opponent's wipe while also surprising them. After this, it is not uncommon to be able to punish them the next turn. Wipes can take a while to set up and so it's actually quite likely to have all the pieces you need when the time is right. I am currently experimenting with more tutors in the deck to ensure that this can happen consistently.
