Markoheshkir is the best magic staff in all of Baldur’s Gate 3. It makes spellcasters better in every way possible, and its only downside is that only one exists. It can’t be bought from any vendor, or looted from an enemy.
To get it, you need a little luck, and a push in the right direction. There are a few things you will need, the first being See Invisibility: some switches are invisible. Second, you need a character with a good Arcana skill.
Ramazinth’s tower
The staff is located inside Ramazinth’s tower in Baldur’s Gate’s lower city. It’s central to the area, and the largest circular building in the zone. When you find it, mention you know about the Nightsong to the merchant at the front. You’ll be directed to the second floor.
From there, take the leftmost portal to ascend the tower. Once at the top, you can use some floating furniture to descend one floor below. There are pedestals with buttons on them placed near the walls. See Invisibility will show you plaques that tell you what they do. You want the one titled “below.”
Getting the Staff
The button will take you one floor down between a pair of arcane barriers. The staff will be in sight, but the switch to lift the barrier is invisible. See Invisibility will help again and reveal the lever.
Pulling the lever requires you to pass a DC 20 Arcana check. While technically possible for everyone, best to have your Wizard do it. If you fail, a statue hits you with a Disintergrate spell. That is very very bad for your health, so use inspiration here if you must. Once you succeed, the barrier drops. Markoheshkir is yours.
The staff is immensely powerful. It raises your spellcaster’s save DC and spell attack rolls by one. It also has the rare ability of Freecast, letting you cast any spell without consuming a spell slot on your character. It also functions as a plus two quarterstaff. Give it to your favorite caster and watch them work.
Wearing The Robe
The robe of the Weave is right across from Markoheshkir, with the exact same release conditions. Pass the arcana check on the switch to avoid disintergration, and you have one of the best mage robes in the game. Wear it.
With its arcane enchantment, the wearer gets another boost to their spell save DC and spell attacks. The robe also provides a two-point boost to armor class. Even with that boost, it still counts as robes, letting you get all the benefits from Mage Armor. Its last ability, Weave Eater, heals you anytime you pass a saving throw against a spell. With both the staff and robe in hand, your caster is ready for the endgame.