No. The effect triggers immediately upon a critical hit if the target has under 100HP. The closest you get to a choice is not using the weapon.

Just got one, helping me fight demons. Pretty cool!

If you score a critical hit against a creature that has fewer than 100 hit points, it MUST succeed on a DC 15 Constitution saving throw or be slain instantly

It doesn't say "you can force it to-" blah blah, it says it MUST. It's not an option.

It's not even rolling a 20 on an attack, it's any critical. So a Champion Fighter could steal lives twice as quickly with it.

Assasin rogue, get the drop on something with under 100hp and done.

I would guess not. It's kinda the purpose of the weapon.

this op never give to party

This thing sucks lol, I wouldn't even consider it a very rare item if I were to use it in my campaigns, it's just a glorified +2 weapon. Rod of security, belt of cloud giant strength, staff of power, arcane grimoire +3, all of these are vastly superior to this trash and yet they're on the same tier.

My campaign group went to the abyss and one of them tried to buy this. It was too expensive, so he tried to steal it. It was valued at 3,500 gp for 2 charges.

I don't see why people make such a big deal about these weapons, apart from the +2 which is pretty sweet, they're garbage.

Anyone you want to use a charge on probably has a high chance to make the middling DC 15 save anyway, and you only get the chance when you get a crit AND they're under 100hp. 3/10 don't waste your money

Every time I implement it *slightly* into the game, my players absolutely go crazy over it, and constantly try and 1 shot my bosses. I had to homebrew creatures to negate critical hits to combat the stupidity that is the nine lives stealer.

Expanded to all weapon types, thats nice.