Fighter Champion critical range and Vorpal Sword

Phantasmal Killer, frightened lasts duration period or until enemy Saves?

Nature’s Wrath and Turn Fey abilities are not very useful

If a Sorcerer casts a spell with only V S components using Subtle Spell, can it be Counterspelled?

If a Sorcerer casts a spell with only V and/or S components using Subtle Spell, can it be Counterspelled?

Can an artificer’s Spell-Storing Item be activated with the Use an Object action, or is it considered a magical item?

Would a Warforged get detected by Detect Magic?