There is no guarantee, ever. You can do 1 reforge and get one, you can do 1000 and get none. Those what krole15 said is the correct answer: "infinity".
There's an expected average reforges, which is probably around 250, as the primal drop rate seems to be about 1 in 250 legendaries from what some people recorded only on last season in spreadsheets, IIRC. But in the end it's all RNG and "guarantee" is never gonna happen.
There is no guarantee, ever. You can do 1 reforge and get one, you can do 1000 and get none. Those what krole15 said is the correct answer: "infinity".
There's an expected average reforges, which is probably around 250, as the primal drop rate seems to be about 1 in 250 legendaries from what some people recorded only on last season in spreadsheets, IIRC. But in the end it's all RNG and "guarantee" is never gonna happen.