In this walkthrough of the Main Story quest “Wand Mastery”, we’ll visit Mr. Ollivander, who will hopefully be able to craft us a wand from the artefacts acquired from the Keepers’ Trials. Of course, this late in the game, it probably won’t be quite so simple.
Before talking with Mr. Ollivander, you should prepare for combat — this quest has an extended battle sequence. Craft Wiggenweld Potions in the Room of Requirement until you’re maxed out (25), upgrade your gear as much as possible, and equip Traits at the Loom that help against Dark Wizards or buff your best combat spells.
Consult with Gerbold Ollivander
This quest begins in Hogsmeade, in front of Ollivander’s shop — the closest Floo Flame is South Hogsmeade. Depending on when you arrive, you may have to wait before beginning the quest. Waiting and starting the quest are done in the same place, the golden circle in front of the shop, and both require that you simply press /.
Weirdly, after you press “Begin” on the circle, it doesn’t actually do anything except allow you to find Mr. Ollivander inside. Walk into his shop, then speak with him by pressing / to begin a cutscene. When it ends, you’ll find yourself kidnapped by Rookwood and taken to what is essentially a battle arena (since you can’t leave until you’ve finished the fight).
Defend yourself from Rookwood’s lot
This is a very long fight, with three “waves” of enemies, and multiple enemy spawns within those waves. Here are some tips to make the fight easier:
Your Spell Diamonds should all have one each of Force, Control, and Damage spells (to break shields).
On higher difficulties: 1 of your Spell Diamonds should have Incendio, Bombarda, and Confringo, plus a Force spell — this is to deal with the Ashwinder Assassin and the Inferi they summon.
Collecting Ancient Magic essence is very important in this fight, especially for taking out the high-HP Executioners. Make liberal use of Accio to bring enemies closer (to make it easier to collect the essence) and focus on not taking damage to build up your combo meter.
The Rangers who hang out on the platforms on the stone arch cast unblockable spells — cast Depulso or Flipendo on them and send them falling to their death.
Once there is only one enemy left in the wave, don’t kill them right away! Instead, cast Revelio and look for any Wiggenweld Potions enemies may have dropped.
Once there are 6 or less enemies in the second wave, stop using Ancient Magic — you’ll want to save it for Rookwood in the third phase.
We encourage you to try your hardest to win without doing so, but don’t forget you can turn down the difficulty in the options menu!
Between each wave, you’ll have to do a button-mashing event where you and Rookwood recreate the classic Harry/Voldemort wand clash — the button is picked at random, so make sure you look before you mash!
Classic
Defeat Victor Rookwood
Victor himself will fight in the third wave of enemies. He has a shield that can only be broken by Ancient Magicand Stupefy, so hopefully you saved up a full Ancient Magic bar! Make sure you’re targeting him (it’s a good idea to push in on the right stick for this) and then press + — follow it up with your most damaging spells before his shield comes back. If you manage to get a few extra spells in after breaking his shield, you should only have to do this sequence one more time (again getting a few extra spells in after using your Ancient Magic).
Note that enemies never stop spawning, so focus on killing Rookwood as quickly as possible. If you can’t kill him with the Ancient Magic you’ve saved, you can either use the Protego+Stupefy counter to break his shield, or you can try to get enough Ancient Magic for another cast — whatever is easiest for you.
After taking away all of Rookwood’s health bar, you’ll have one more button-mashing wand showdown, and then he’ll go poof, ending this quest. Now you’ll need to return to the Keepers with the wand Mr. Ollivander crafted.
Unabashed FromSoftware fanboy still learning to take his time with games (and everything else, really). The time he doesn't spend on games is spent on music, books, or occasionally going outside.
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— follow it up with your most damaging spells before his shield comes back. If you manage to get a few extra spells in after breaking his shield, you should only have to do this sequence one more time (again getting a few extra spells in after using your Ancient Magic). 
