This build is not meant for combat, but it will be very good in what it’s meant for, and that will be Persuasion, Sleight of Hand and Stealth.
With this build you can get to 100% success rate at stealing things since it can get you to DC 30 (minimum) in SoH in this way: +10 base (from the “Reliable Talent” passive at L11), +17 SoH, +1 from Guidance, +1 from Shapeshifter Ring (when you’re Camouflaged), +1 from Bardic Inspiration/Hide Armor +1.
If you choose Astarion like i did in this build, you can switch Bardic Inspiration for his “Happy” passive for the same result without using Bardic Inspiration Charges. In that case you can switch L12 Bard for whatever you prefer.
Another perk of this build is that you can get to a whopping +38 Stealth (minimum) in this way: +10 base (from the “Reliable Talent” passive at L11), +15 Stealth, +1 from Guidance, +1 from Shapeshifter Ring (when you’re Camouflaged), +1 from Bardic Inspiration/Astarion’s “Happy”, +10 from Ring of Shadows (equip the ring, use the ability, unequip the ring).
This way you can get to 4 check of Greater Invisibility in Honor Mode with 100% success, even 5 checks if you roll more than 1 on Guidance and Shapeshifter Ring (5 checks is DC 40), and basically permanent uptime in Tactician and below since Greater Invisibility doesn’t scale exponentially like in Honor Mode.
The only downside if you want to use Greater Invisibility is that you need another party member to cast Greater Invisibility on you since you’ll already be Concentrating on Ring of Shadows ability, and another one to Concentrate on Guidance.
