The Unearthed Arcana Paladin class ability "Channel Divinity: Guided Strike" says:
Guided Strike. You can use your Channel Divinity to strike with supernatural accuracy. When you make an attack roll, you can use your Channel Divinity to gain a +10 bonus to the roll. You make this choice after you see the roll, but
before the DM says whether the attack hits or misses.
When a paladin strikes an opponent who is able to cast Shield, who has to announce first whether Guided Strike/Shield is used? I am assuming I cannot wait until the DM announces whether he uses Shield or not to announce my own Guided Strike?
Best Answer
The Paladin calls it first
Guided Strike has to be used before the attack is declared a hit or miss. The Shield spell can be used after the attack hits (so it will always turn a hit into a miss, if used correctly).
You use Shield after the DM has declared the hit. Contrast this with Guided Strike: