Even if you weren't impressed by the ending of True Detective's first season, the occult altar that appears in the season's final episode is wonderfully horrific, and is filled with details we couldn't fully appreciate in the show. Spoilers below.
Artist Joshua Walsh crafted the altar in Carcosa, using narrative details from the show to create a monstrous figure of driftwood and bone. He fixed a cow spine to the figure to give it a sort of bestial quality, with driftwood for the arms.
Oyster shells fill the area, and Walsh used turmeric to set off the spiral symbol on the main skull in yellow. According to Walsh, the pairing of oyster and turmeric "created this spicy, death smell" on the set.
Walsh also added charms to the tree, small toys that he imagined the killers might have found in a schoolyard.
Walsh would build the lattice work around wrappings, which he calls "spirit bundles" to create smaller shrines within the altar.
The wooden star hanging over the sacrificial rock is made of burned driftwood, a nod to the killer's charcoal drawings.
You can see more details from the episode at HBO's True Detective site.