So this deck has a number of different strategies in it, most of which help feed into each other.
"Mikeaus, the Unhallowed", "Grimgrin, Corpse-Born", and "Grave Titan" are all the game enders themselves. On top of that, these 3 feed each other. Titan gives fodder for "Grimgrin, Corpse-Born" and that fodder can be brought back with undying from "Mikeaus, the Unhallowed".
If you have both "Diregraf Captain" and "Grimgrin, Corpse-Born" on the field, then together they become a burn engine (+ creature removal)
Note: "Geralf's Messenger" also fits into this perfectly. when you summon him, opponent loses 2 life, then if he dies, he comes back stronger, and your opponent loses 2 more life, +1 extra for each "Diregraf Captain" you have on the field
"Gravecrawler" is also fodder for these engines, is a low mana attacker for early game, and can bring itself back. Also works great with "Diregraf Captain" to just attack by itself. 3/2 zombie, and if it dies, your opponent takes a damage, and you can summon it right back to go again next trun for only 1 mana.
"Cemetery Reaper", "Diregraf Captain", and "Mikeaus, the Unhallowed" build up creatures. With a total of +10/+10 possible in the deck.
"Call to the Kindred" gives you a free zombie every turn! You can even enchant your "Diregraf Ghoul", and next turn lay down a "Grimgrin, Corpse-Born" or "Mikeaus, the Unhallowed" for free!