Yes, you can use your reaction to cast another spell so long as it does not require concentration.
Is true polymorph permanent?
True Polymorph isn’t permanent, as in you cannot ever dispel it or avoid suppressing it, because it remains an active spell with a duration and ending qualifiers.
Can permanent true polymorph be dispelled?
A permanent magical effect can be dispelled unless the spell explicitly clarifies that it cannot be. True Polymorph fits into this category, which means that it can be dispelled.
Can true polymorph change gender?
A True Polymorph spell’s wording says that you can change the object or person you’re casting the spell upon in to any creature you want. Specifically, the description says “the new form can be any kind you choose.” So, it would appear that if you wanted to change a human male in to a female dwarf, you could.
Do you know the roll for a shield spell?
According to Sage Advice, the caster should know the roll made for the attack before casting Shield. There were some that argued that the caster should not know the roll and should cast Shield before seeing if the spell would block the attack or not, because it was metagaming too much to know the roll.
Can a spell be cast before the barrier of force is created?
The counter argument was that if the caster was able to cast Shield in time (the moment before impact, before damage can be rolled), then the barrier of force created by the spell would block the attack, so if the attack was going to hit anyway, the caster would not have had the chance to cast the spell in the first place before getting hit.
Do you have to know the roll to cast shield?
There were some that argued that the caster should not know the roll and should cast Shield before seeing if the spell would block the attack or not, because it was metagaming too much to know the roll.
How do you end a fire shield spell?
You can end the spell early by using an action to dismiss it. The flames provide you with a warm shield or a chill shield, as you choose. The warm shield grants you resistance to cold damage, and the chill shield grants you resistance to fire damage.
