Balor's Fire Whip

Finesse. 1d4 slashing + 2d6 fire damage, 10ft.
Bright light 40ft, Dim Light 40ft.
Once per short rest, on successful attack, add extra 2d4 damage & opponent up to 1 size
larger than you rolls a Strength saving throw or falls prone. DC 8+Prof+Str/Dex (your choice).

If you roll a nat 1, the whip's voice is too strong.
Attempt a DC15 CHA saving throw.