Minor changes.

Implemented natural spawning for mobs, fixed NPE where a mob would walk
into a leech life projectile and then it would try to move in the same
tick, changed mana regen mechanic to be quicker with a higher mana cap,
changed the vampiric wand to have its' type discovered on use and not
equip and made stairs not say the "can't walk into me" message when mobs
walk into it.
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