Prefatory Remarks and General Strategy:
Do you want to play a strong, independent angel that don't need no man? Bruna, Light of Alabaster is a powerful Voltron commander that is capable of sealing up games quickly when she gets online. Combine this with her Blue-White colour identity and you can turn any board-state into her own personal wasteland where she reigns supreme. Blue and white makes her very easy to defend.
This is a Control & Stax deck that strategically uses control elements such as counter-magic and removal (both pinpoint removal and mass removal) supplemented by powerful stax and hate cards to set up a lethal Bruna swing while severely disrupting your opponents' strategies. It can either play a very quick game (potentially setting up a turn 3 lethal Bruna swing) or a much longer game. The card quality of your bombs is extremely high under all of the stax elements at your disposal.
Lightning Greaves is all that you really need as a haste outlet. There are plenty of ways to tutor it. Having no haste outlet is no big deal given the counter-magic and stax elements in the deck to slow down matches and make you harder to disrupt; (but it's always nice to have one around). Vanishing, Spectra Ward and Gift of Immortality serve to protect Bruna. Vanishing is by far the best protection that you can get in the deck since it allows you to easily respond to targeted removal and mass removal.
Bruna can slay your opponents in a number of different ways. Any two-aura combination of Eldrazi Conscription, Corrupted Conscience or Battle Mastery is lethal damage in one shot. Having Steel of the Godhead is particularly good on its own in 1v1 to provide a three-turn clock supplemented by lifegain. It's mainly in the deck to recuperate some lost life since this deck does hurt itself a lot. Eldrazi Conscription Battle Mastery and Steel of the Godhead in addition to a form of protection is quite a powerful creature for your opponents to contend with. She is effectively healing you for 34 every damage step alongside killing a player.
Have you ever seen an Elvish Mystic kill with Corrupted Conscience and Eldrazi Conscription? In my world, this shit is possible. Sovereigns of Lost Alara and Starfield of Nyx avail such strategies. They can turn any one of your hatebears, which are already seriously disrupting a lot of your opponent's 'competitive' gameplans, into pseudo-Bruna. You can save the real Bruna for later.
Plenty of artifact ramp is included in order to speed up the deck. The deck's consistency is availed by a lot of draw and tutors. There are recursion engines in the deck to take advantage of discarding from cards like Jace's Archivist and Windfall. and Bruna herself pulls auras out of the graveyard. This makes Intuition equivalent to Three Dreams.
Cataclysm seals up games at that point.
Tips to the Deck:
The two golden rules of the deck are that (1) patience is a virtue; and that (2) you will become the target when you cast Bruna so get ready to become the archenemy. With a note on rule (2): your political game up until that point is to disrupt your opponents' strategies whilst not doing anything that would draw too much attention to yourself. It is one thing to wipe a Yisan player's board under the context that you were saving the rest of the table as well. It is another thing to be broadcasting that you want to race for the win by preparing mana batteries and tutoring with your early turns. You would be broadcasting too much information to everyone and you would consequently be painting too large of a target on yourself. The trick to landing an utterly unanswerable Bruna is by picking your moments. Patience is a virtue and it is often better that you wait to gather all of your pieces than just playing them out onto empty boards.
If you want to play some of your pieces out (under the pretense that, say, you want to make the most use of your mana each turn), then either (1) play them into 'clogged' boards where there are multiple, more pressing threats that need to be dealt with or (2) deflect your threat levels onto another player through politicking and rhetoric. This is risky given the ubiquity of board wipes in the format, however. The advantage to the way that Bruna works is that she can be difficult to read at times (example: Intuition on an end step with Greaves on the table already leads to a 1.5 turn-cycle Bruna kill). People will tend to pay less attention to your greaves when there is a Consecrated Sphinx on the table.
The key to piloting the deck in multiplayer politics is how and when you broadcast an advancement of your core strategy. This is true for any combo-oriented EDH deck as well. Employ that sort prudence with this deck as well. Otherwise, disrupt the board through hard stax to simply make Bruna unanswerable to begin with and go from there.