The question of mana isn't fully answered once you've decided how many and what types of lands to play
Collectors pay more for rarity, whether that rarity comes from limited prints or difficult-to-grade quality
While theyre useful to ramp out massive artifacts, they also work exceptional well in storm and similar archetypes that attempt to cast a flurry of artifacts by making 1- or 2-mana artifacts cost 0
Mostly, this gives you a Zombie at the end of your turn if you lost 2 or more life, and losing life on your own turn isnt something that will just happen -- youll have to create situations to make that part work, and even though Black is always capable of doing that in Limited, it is highly unlikely you get a critical mass of those cards going that allows you to consistently make a Zombie, and you probably need to get at least two out of this for it to feel worth it
Not including the static ability ones from War of the Spark that only had one minus ability, only Ajani, Caller of the Pride, Gideon Blackblade, Teferi, Time Reveler, and Vivien, Champion of the Wilds have at least 4 starting loyalty
Tracking down rare Japanese cards individually can be challenging, as they are frequently scooped up in the West