Blightsteel

[Avodroc13]

 {Primal Huntbeast} + {Primal Visitation} +
{Titanic Growth}(x2) vs  {Blightsteel Colossus} would send it to the graveyard (technically into its owners library) -- Correct?

[TreeTopSky]

Incorrect. As the ability 702.12b Any damage that would be considered lethal does not affect the object.

[Avodroc13]

----the guy that answered is the guy I'm talking about who had Blightsteel. Can someone please justify this?

[Quisequise]

Since Blightsteel is indestructible it would not be sent to the graveyard.

702.12b: A permanent with indestructible can't be destroyed. Such permanents aren't destroyed by lethal damage, and they ignore the state-based action that checks for lethal damage (see rule 704.5g).