Grixis Delver is a tempo deck that utilizes hand disruption and kill spells to clear the way for low-cost threats. 

Thoughtseize and Inquisition of Kozilek are similar cards that both have strengths and weaknesses. The life loss of thoughtseize means that it is only of 3-of in the mainboard. This is because the manabase is quite painful with all of the fetch lands to fix your colors. 

The deck runs many kill and burn spells to keep the board clear for its threats to connect. A thing to note is because the deck is so low to the ground, the ways to deal with large creatures are limited. Unholy Heat is the best way to deal with large creatures such as Primeval Titan. For the counterspells instead of needing two blue mana for Counnterspell or putting it on top with Memory Lapse this version of the deck runs Change the Equation. This hits most of the spells in the format with the main outline being Treasure Curise. Most of the larger spells in the format are either green or red so it is a more mana-flexible version of a hard counter. 

As for threats, the monkey makes an appearance to provide card advantage and force your opponents to answer it turn one of the game. When on the draw in a sideboard game 2-4 Ragavans should be sideboarded out. Because without Ragavan the deck is somewhat light on ways to win the game there are three Ledger Shredder s. While the connive triggers can be turned against you with bowmasters, the 3 thoughness which grows means it is not as vulnerable to bowmasters as Ragavan or this deck's orchis bowmasters. Dragon's Rage Channeler is the final threat of the deck. To support it with delirium as well as giving surveil triggers is a playset of Mirshra's Bauble. The baubles also fill the graveyard to escape the one of Kroxa, Titan of Death's Hunger. This is terrible in multiples so it is a only one of, but it provides a late-game threat that is resistant to removal. 

In this particular deck's sideboard, there are three Blood Moon s. While it is incompatible with the companion it is incredibly valuable against the most popular deck, TitanField. Additionally, there is an additional counterspell for the troublesome deck as well as two Molten Collapse s to be hard removal for decks with large creatures or numerous planeswalkers. Pithing Needle Also deals with Planeswalkers, Necropotence, and can be used to shut down fetch lands against unsuspecting opponents. Cast into the Fire is a decent piece of tech for the mirror match as most of this deck's creatures are X/1s as well as dealing with decks utilizing The One Ring. 

Other versions of this deck run Deathrite Shaman As well as a green and X land to be fetched into. It provides more resistance to Bowmasters and is graveyard hate. Death's Shadow is also an option. Fetchlands and Shocklands as well as the damage from Thoughtseize mean you will be burning yourself for ~5-7 Damage per game unless you are playing very conservatively with your life. Death's Shadow capitalizes on this by providing a late-game threat. Some decks even play the MDFCs from Zendikar as well as more spells that pay life just to enable death's shadow as early as possible. I belive, however, that your life total will become low naturally throughout a game, and paying extra life for everything makes it difficult to save your life when you need to.