My take on UB Delver.

I figure the deck always needs a card draw engine in addition to Thought Scour/ Mental Note /Brainstorm, and that the heart of this deck is protecting the Gurmag Angler, and the flying clocks, be them Delver of Secrets or - in some decks - Sultai Scavenger .

Combining this, I'm running Mulldrifter as the combined additional card draw engine AND flying threat, and Undying Evil as additional protection for my creatures AND a crazy-fun-combo-card-draw-engine: t4, Evoked Mulldrifter + Undying Evil = 4 card draw and a 3/3 flying beastie!

Undying Evil also protects the Gurmag Angler and means you can trade Angler for Angler against MBC, and come out with a 6/6 Stinky Fish whilst your oppo gets nothing.... The only lack of pure synergy for Undying Evil is with the Delver of Secrets . Still, if you Undying Evil a flipped Delver it comes back as a 2/2, and stays on board with a chance to become a flipped 4/3 flyer (thats right, the +1/+1 counter stays after the flip) - which is better than it sitting in your graveyard!

As I'm only running 4 creatures which use the delve mechanic I 'only' run a total of 6 Thought Scour / Mental Note , and have given 2 slots to Ponder to help with the Delver of Secrets flip and general digging. I never have a problem, due to an under stocked graveyard, in casting a Gurmag Angler or destroying with Ghastly Demise .

The Disfigure is cheap early removal, which I prefer to Agony Warp, which I find to clunky due to its BU casting cost. The Ghastly Demise are absolute beasts often able to deal with any toughness (non-black) creature at instant speed, hence 4 of in my primary build. Granted, they are dead verses MBC, so 4 anti-MBC'ish cards must be included in the SB (Edicts, perhaps?), and dependent on the prevalence of black in the meta the amount of Ghastly Demises may need to be reduced accordingly.

Finally, the counterspells, where a full playset of Counterspell is mandatory, with an 'additional 2' in the form of Deprive . Most of the kill, burn, and counter spells at pauper are instants, so 2 Dispel helps protect further for a low casting cost. Dispel is great at countering an opponents counter, where the single B mana cost is critical.

Anyway, all thoughts and comments are welcome, especially any suggestions to make the deck more competitive, and to create a SB, :-)