Piercer feat from Tasha’s Cauldron of Everything states that on critical attack roll you add an additional weapon damage die to the damage roll. Does this extra dice also double on a critical hit?
Ex: Critical hit with dagger with Piercer feat would be 2d4 + 2x1d4 (piercer feat) = 4d4
or is it just 2d4 + 1d4 (piercer feat) = 3d4
Build a fifth Lv Rogue Swashbuckler who suffered the initiator's magic on Lv4 to inflict additional damage with Booming Blade and Green Flame Blade.
Using a regular rapier with Booming Blade on the current Lv, he was able to pull a sneak attack and inflict 1d8 damage + Dex Mod, + 1d8 Thunder damage and 3d6 Sneak Attack.
Do all the dice double on a critical n "Nat 20"? Would the litter have a total of 2W8 + Dex Mod + 2W8 Thunder Damage and 6W6 Sneak Attack Damage?
So would this be an example of a weapon attacking, criticizing a spell and abilities?