Howdy,

As said before, I tried a version of UBR Grixis with two-three copy of Abrupt Decay (because I was already running a single Tropical island).
At first, in the side, but as I was almost bringing it in on every match-ups, so I quickly opt to move Abrupt Decay in the main.

Then, I figured that 3 copy was a bit too much, as more often than not, I cannot play Abrupt Decay because my firsts lands were UB and UR (I play with 2 Grim main instead of Tombstalker).

With 2 copy, things were much more good. With the free slot from one Abrupt Decay and one from running 12 instead of 13 creatures, this let me play with two Dack Fayden.
Dack let see you more card, and really fit with Grim Lavamancer ( or Tombstalker). Dack's Ultimate isn't that powerful, but can make sometimes huge things.
Sadly, Daze become a bit worse with all that 3cmc cards. I chose to run Spell Pierce instead. I still dont have enough games to tell if Spell Pierce really worth the change.

Here is the list I'm currently playing :

//Creature (12)
4 Deathrite Shaman
4 Delver of Secrets
2 Grim Lavamancer
2 True-Name Nemesis

//Instant (20)
2 Abrupt Decay
4 Brainstorm
4 Force of Will
4 Lightning Bolt
2 Spell Pierce
4 Stifle

//Planeswalker (2)
2 Dack Fayden

//Sorcery (8)
4 Gitaxian Probe
4 Ponder

//Land (18)
1 Badlands
4 Polluted Delta
3 Scalding Tarn
1 Tropical Island
3 Underground Sea
2 Volcanic Island
4 Wasteland

SB: 2 Ancient Grudge
SB: 2 Deathmark
SB: 2 Fire Covenant
SB: 1 Grafdigger's Cage
SB: 1 Nihil Spellbomb
SB: 2 Pithing Needle
SB: 3 Pyroblast
SB: 2 Surgical Extraction

Mainboard is really good. Personnaly I prefer Grim (more control) over Tombstalker. With Dack emblem, Grim is also a way to steel opponent creatures/planewalkers, while Dack's +1 Ability feed the yard.
Pyroblast is an awesome card against every blue deck, and give one more way to target opponent permanents.
The rest of sideboard is still under reflexion, especially the Grave-hate. I used to play Grafdigger's Cage, but I'm looking for more permanent answers, because Shaman already act as soft grave-hate.
Any feedback really appreciate :)