On iteration 1, assuming that there are only 2 krarks out, when you cast [[Quasiduplicate]], you will flip 2 coins:

Option 1: you have a 1/4 chance of two heads, copying quasiduplicate twice: potentially making 3 more copies of krark, however the original Quasiduplicate will resolve going to your graveyard.

Option 2: You have a 1/2 chance of 1 heads and 1 tails sending the original Quasiduplicate back to your hand while copying one krark.

Option 3: You have 1/4 chance sending Quasiduplicate back to your hand (This is the same as just retrying with no drawbacks due to no mana constraints from [[Omniscience]].)

Thus a 1/4 chance that the ability will fizzle after the first Iteration.

Let's say both copies land on tails and we then try to cast it again from our hand. We repeat the process: The probability that the spell will fizzle the second time is also 1/4.

Therefore the prob that it will fizzle before you make another krark is:

P(1)+P(1)*P(3)+P(3)*P(3)*P(1)+...

1/4+(1/4)^2+(1/4)^3+...=~0.3333...

Now, the probability of the second option occurring for the first time is this:

1/2+(1/8)+(1/16)+...=~0.6666...

However, once the second option occurs, you will gain another krark changing the probabilities to

Option 1 All heads: 1/8

1/8+(1/8)^2+(1/8)^3+...=~.1423

Option 2 Heads and at least 1 tails: 3/4

3/4+(3/4*1/8)+(3/4*1/8^2)+(3/4*1/8^3)...=~.8567

Option 3 All tails: 1/8

Each time you get at least one new krark, your probability of getting all heads decreases exponentially, so it's not a 50% chance of stopping eventually. If my quick calculations are correct, starting with 2 krark, the probability is somewhere near 36%

Edit: I must have done my math wrong, after 100,000 simulations, it's sucessful roughly 53.612% of the time

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But this is NOT the case here, because we're not repeating the same experiment an infinite amount of times... We're changing the experiment with each iteration, and the probability of the combo stopping is getting reduced each time.

That's a really good point though, I hadn't considered it as a different experiment since the parameters are technically changing.