I do have a few suggestions that may help in the strength of this deck build:
1) You might want to side board
Oath of Nissa. If Ob Nixilus is not going to be main board then it shouldn't really be a crucial part of the deck.
2) Call of the bloodline you may want to switch with
crawling sensation (since the second effect triggers naturally) and you can combo that with
Morkrut necropod and
cryptolith rite (for mana producing and sac targets for your slug horror).
3) If you replace the
mindwrack demon with
hound of the farbogs AND
might beyond reason then you'll have a menacing creature with high stats.
4) Also
rabid bite and
stoic builder would be good creatures and spells to add since they help with the land recursion and your stronger creatures can remove small threats without having to swing (sort of like
prey upon).
5) Also the Hydra and the Frog work in
opposition to one another. Either one can work in this B/G
delirium deck depending on how you build it but having a creature that requires for you to sacrifice land and a monster that gets stronger BECAUSE of your lands is not the best idea. If anything, cut down the frog horrors down to two and only play with either 2x frogs, 2x hydras or one of each. This way their effects are not working in
opposition to one another and the deck flows better. Also if you're going to use the hydra find ways to bounce it back to your hand or
recycle it from the graveyard for repeated uses.