To strengthen the combat power of the undead, there are six creatures in the deck that give zombies +1/+1 or +1/+0: Diregraf Captain, Lord of the Accursed, Lilianas Devotee, Death Baron, Cementary Reaper, and Tomb Tyrant
Im very strict when it comes to giving more than one point though, as I wouldnt recommend only 5 cards for card draw, even if they are exceptional, due to the fact that you must keep the chances of having access to them high and avoid to depend on only a few cards because you can be a victim of a removal spell
Lands care about legends too so Monumental Henge can help you dig for walkers while Untaidake, the Cloud Keeper, and Plaza of Heroes help you play your planeswalkers
Inspiring Refrain draws two cards and then returns every few turns, which helps fuel long-term card advantage and sets you up for big turns
But if you want a card that does even more damage, look no further than Prince Phillip
Whenever this creature attacks, return target nonland permanent card with mana value X or less from your graveyard to the battlefield, where X is this creatures power