Defensive mostly.

Aegis is 1925g total.
Gives 250hp.

+23armor aoe, +24 mr aoe. +10 damage aoe.

At level 10 or so, 23/24 ar/mr is quite a bit. A noticeable change in survival.
+10 damage isn't huge for you. But again the earlier you get it, the more it does matter. And +10 damage to npcs is massive. I don't have the numbers in front of me, but I think that basically double their damage mid game.

Emblem is 800g
17% ls, and 10hp/5s regen for just you.

Starks is
1750g over the cost of emblem.
It gives 20% ias to you.
20% ls aura, 25% ias aura -25 ar aura, 30hp/5s aura
So, total for you is 20%ls, 45%ias,-25ar aura, 30hp/5s
(-25 ar aura doesnt effect towers)

effect -emblem. 3% ls, 45%ias, -25ar aura, 20hp/5s.

ls,30/hp5s, and 25% ias wont effect minions as much as the ar/mr and +damage will.
You get most of the LS, and the armor/mr which gives you more survival.
Starks is more damage, and the hp/5 is good ooc, but not really meaningful in combat.
Also trivialized if you a healer on your team.
The armor pen is nice, but doesnt effect towers.

Caster teammates would get more from the ar/mr then the ias/ls too, if your team is more caster heavy.

I'm not saying its flat out better. its not. Its just a choice you can make, depending on how the game is going, and your own playstyle.
An aegis+emblem Sivir is alot harder to kill then a starks sivir.

Aha I see.

Im glad you said its not better. I think we all agree that Level 2 OTH + starks and a 5 man push at around the 16 minute mark is by far the most powerful thing she can do.

Id also like to mention, I have yet to see ANY champion that DOESNT auto attack. It may not be as large a damage boost as on a physical DPS, but do not neglect the increased attack speed and lifesteal for the casters.

More importantly, remember that 40% of AP goes towards tower damage on your auto attack. That increased attack speed coupled with that extra tower damage can lead to some pretty amazing DPS to the tower by the caster.

Lastly, and this is a REALLY big part of it:

The cost of Starks, for just its benefits it grants you, is worth it! The 700 gold combine gives you 20HP/5, 3% lifesteal, 5% attack speed and -25 armor to enemy champions. Id buy that for 700 gold.

So considering that, if you have even 1 other physical DPSer on your team, its better to go with starks. The only time I wouldnt get straks first is if I was paired with 4 pure nuke casters. Of course, in that case, I wouldnt have picked Sivir. I would have picked Alistar as he is better for caster auras. You still get aegis, but you also get soul shroud and possibly locket. Works rather well.

Oh, and Mbirk, emblem regen is an aura as well. Minor I know, but best to clarify so new players dont get confused.

Thoughts on boots and rally:

Boots, I typically get mobility, but I notice that most people get zerkers. IMO, mobility is MUCH better for this particular champ. Agree?

Rally... I've gone away from rally recently to improved fortify. Essentially, fortify isn't worth getting without the mastery because it wont deflect a creep push. Improved fortify will stop a creep push, but it also screws tower divers, and at least twice each game stops a real tower push, which delays their team the extra gold/xp which could easily start the snowball. Sure they might get the tower eventually, but delaying the other team from getting stronger is keeping your team ahead that much longer.

Rally seems good on paper, but it rarely gets used effectively. A) The range is short. VERY short. If the fight moves even slightly away from the point of initiation, its worthless. B) Long cooldown, prone to false alarms. Team fight initiates, you drop it, either side backs out - wasted. C) If you manage to drop it at the right time, and your team stays in it, and the other team doesn't kill it - still it only 'synergizes' with physical dps.

I dunno, every time I look at rally is looks so good in theory that I think about switching back, but then I remind myself why I stopped carrying it. Fortify - always useful, Rally - sometimes very useful.

First, I'd like to thank MOgri as well as QUICKSLIDE for all the input to the Sivir community. I just started playing her a couple days ago and going off the advice in this guide I've been tearing it up.

Zingle, I kind of wonder the same thing. I've been running with Rally and I rarely use it simply because the effect is situational. I do push hard with the team as is, and any little bonus is currently helping I guess, but when you're playing Sivir and you have poorer players anchoring you down I always think that Rally is a wasted spot. I'm very curious about the answer to this as well.

On Boots:

Boots, regardless of champion, are ALWAYS situational. The options for Sivir are Zerks, Mercs, Swift and Mobility. Any of them will work fine.

The reason we put Zerker boots in the list is, its the optimal option. If yuo play this strat well and its working for you, the Zerker boots will help you finish that inhib early where as the rest wont.

That being said, if your not dominating, you may want to look at the other choices. Of course, generally boots arent really discussed as they are pretty self explanatory. Too much CC on oposing team, get mercs. Enemy team pushing as fast as you are, get mobility. Pushing by yourself a lot, get swiftness (so you have a better chance of running).

So if your having better luck with mobility, thats fine. I personally dont take them because I find teleport does the job and I am pretty much ALWAYS incombat. Sivir is not a ganking champ that is constantly running between lanes.

On Rally:

I wouldnt even dream of not taking rally. It is, by far, the most powerful summoner spell on Sivir. It has many uses. Early game heal, teamfight boost and all that good stuff.

But there is one particular scenario where rally REALLY shines and I am SURE every single Sivir has run into it:

You got your starks, you 5 man pushed your lane and your staring at the enemies inhibitor tower and all 5 enemy champs. What to do. Well, generally you wait on the next creep wave and move in to attack the tower.

We have a problem of course. There are 5 enemy heroes killing creeps and attacking you. None of you want to attack the enemy champions and take tower fire. Well Rally actually solves all of these problems.

The first thing it does is gives your team courage. Everyone knows what a rally does. Youd be suprised how many champs (and players) KNOW they can down a tower very quickly with just a little extra damage and some defense while they do it. Rally provides this. Maybe that Yi who just wont run in will see the rally and know he cant get that tower down now. Maybe your alistar realises that between his abilities, ult and rallys heal that he can tank the enemy tower and all 5 heroes and finally engages. Whatever the case is rally will often give your team that extra push they need to go after the inhib tower.

The second thing it does is increase your teams damage by a LOT. Your Sivir! You have starks, you probably have your ult going! Adding 20 damage to each champion on TOP of the attack speed your giving them (and lifesteal) makes a HUGE difference. Drop your rally, run in and start nailing that tower! Your teamates WILL follow suit. The best thing about it is, your oponents will quicjkly see that the tower WILL go down and more often then not, one or two will run off to do something else.

Lastly that heal is incredible. Again, taking the inhib tower and the inhib it is crucial. I find that the difference in my games where we take that first inhib and then eed to go push another lane as oposed to the ones where we take the first inhib and roll right on through the nexus is Rally! 15 seconds while your knocking down the tower and the following inhib combined with starks 30/5 HP regen and the lifesteal you give to your team will keep them in fighting form! This keeps your push going and, more often then not, convinces the enemy carry that they shouldnt try to instagib one of your teamates and then run away (that is, in general, what stops a final push more then anything else).

In any case, that battle for the inhibitor tower is a defining moment of Sivirs game and NOTHING will help as much as a rally.

Aside from that its great in any teamfight. Yes the fight will move, but chances are thats because you dropped your rally, your team killed a couple of oponents and the enemy is now running away. Hell sometimes one of the oponents SEES the rally and decides that it would be best to back off and fight the teamfight away from the flag. Of course, he doesnt tell his teamates and it loses the teamfight for them. There are a LOT of scenrios like that where rally can be a deciding factor.

In addition it gives INCREDIBLE pushing power. I pretty much ALWAYS push the first mid tower at level 6 with a rally flag. You just march up with your creep wave, ignore the enemy champion, drop the flag, pop your ult and go to town on the tower. It WILL go down. I do of course try and send the eemy champ back (or kill them) first, but as long as they are low enough on health to be warry of you, you can easily take that tower with your ult and rally.

Lastly, it gives me about half of my early kills. A good half of those kills is on tristanas. All it takes is being around 1/3 health and tristana WILL jump you to engage. Drop rally activate potion, throw BB and then auto attack them to death. Works every time and you end the fight with full health and can then get some good damage in on the tower. It can also be used as a normal heal early on if you screw up or suffer a gank attempt and, believe it or not, it heals more then the summoner spell heal.

As to when you have scrubs for teamates. Chances are you probably still want rally. Why? Because while your scrub teamates are desperately trying to defend your base from the enemy teams push, you with this build and your rally can push just as fast, if not faster then all 5 enemy champions (faster if your teamates are dong anything to slow them down). Rally here again is huge and it has to do with the inhib tower and the inhib. Sivir with teleport and rally can backdoor the tower and inhib before the enemy can get there (short fo their own teleport, you will still kill the tower though, just not the inhib).

On Fortify

Im not a fan of fortify in general. I find the cooldown is WAY too long to be of any real use. Its doubly useless on Sivir though as you really shouldnt be fighting at your towers. It is too easy for Sivir to waltz into a lane and spend 3 seconds annihilating the wave to get the eb and flow of the waves moving towards the enemies base instead of yours. Early game its of little use to you because honestly, if your getting pushed to your tower as Sivir, your a teribad and Sivir is not for you. Its far too easy with her to push so you should never have your own tower in danger.

I feel like fortify is planning for failure. Id rather take something that can not only help defensively (Sivir guarding a tower with a rally ready is NOT losing that tower) as well as offensively (as we covered earlier).

I think the most difficult part of this strategy and accompanying build is when your playing good oponents who know that the inhibitor tower is the best place to stop your push. Rally is the only summoner spell that is really going to win that for you or at least tip the favor into your corner enough that either your teamates rally to the cause or the enemy flees at the sight of your war banner.

In the end though, your the danm Battle Mistress! Why wouldnt you carry around your very own inspiring battle standard!?!