The description of the Sanctuary spell (PHB p 272) says:
You ward a creature within range against attack. Until the spell ends, any creature who targets the warded creature with an attack or harmful spell must first make a Wisdom saving throw. On a failed save, the creature must choose a new target or lose the attack or spell.
The description of the Sentinel feat (PHB p 169) says:
When a creature within 5 feet of you makes an attack against a creature other than you…you can use your reaction to make a melee weapon attack against the attacking creature.
If a character with the Sentinel feat is also warded by Sanctuary, and an attacker fails the Wisdom saving throw and attacks a different target within 5 feet of the character, will this still trigger the melee attack reaction?
Best Answer
Yes, the attack being caused by Sanctuary will not prevent it from triggering Sentinel. You've already quoted the important rule:
There's no conditions placed on this. If a creature within 5 feet of you makes an attack against a creature other than you, you get your reaction to hit them. It doesn't matter what kind of attack, it doesn't matter what caused the attack. Any attack triggers Sentinel.