How do you get the Harrowing 2013 - Spirit of the Altar?
It was a mission or event reward. Riot's description in the client reads: “Earned by purchasing any Harrowing skin or ward skin.”
Is the Harrowing 2013 - Spirit of the Altar still available?
No. Riot tied the Harrowing 2013 - Spirit of the Altar to 2013 (mission reward), and it does not normally bring back past event rewards or bundles.
