first : ☆Barrier Thorn Nirvana
where it loses its range for interval. probably an error when the devs made them but it made everyone (sins) happy. this stage is the recast stage.
2nd: ☆☆Dark Death Thorn
this one has completely random stats. 1 major and 2 minor stats. it does NOT keep any stats from the recast. this is the quenching stage.
☆Unconsciousness also have 2 stages:
☆Unconsciousness Nirvana
this stage changes no attributes. it raises damage and (according to pwdatabase) raises the damage received from refines, though the weapon grade stays the same.
2) ☆☆Netherworld Guidance
this one has completely random stats. 1 major and 2 minor stats. it does NOT keep any stats from the recast. the only difference between this stage and the barrier thorn's final stage is the look of the weapon
☆☆Relentless Finisher turns into ☆☆Dark Death Thorn skipping the recast stage altogether.
all this means is if you have the TT100 weapon you need less rapture stones to get to G15 Nirvana weapon.