@JeremyECrawford if a player diviner wizard uses Portent to replace an enemy roll, can the enemy diviner wizard replace players roll with Portent?
— Anthony Harris (@AnthonyHarris97) February 19, 2018
Different wizards can use Portent (a School of Divination feature) on the same roll. See Xanathar's Guide to Everything (p. 77) for guidance on how to adjudicate simultaneous effects like that. #DnD https://t.co/qkeUx3hD0n
— Jeremy Crawford (@JeremyECrawford) February 22, 2018