He may be nearly twice the price of Atraxa, but green/black decks can easily ramp or reanimate him out early on
While I do have my concerns about the scaling of this card I think it is very suitable for both aggressive decks and control decks
If you want a more devious way to build Kelsien, slap on him a Thornbite Staff, which lets you untap Kelsien each time a creature goes to the graveyard
The story of Duskmourn: House of Horror has been published in its entirety, with a main story focusing on rescuing Nashi and side stories that showcase other parts of the House
It's only one color, so you can slot it into probably any Elemental deck (you better be playing Green!)
Circling back to TAUC costs, you could argue its actually even closer to free than other alternate costs: life points and cards in hand are expendable resources, and (at least for drawing cards) somewhat expensive to replenish