So you are definitely incentivized to get him to a location and then you can just start questing away with him
Cards like Sanctum Weaver, for example, can tap for a lot of mana, and even if the Creatures themselves die, you can still activate their abilities, just as Enchantments
By converting your life gain into +1/+1 counters, he ensures that each Food you eat also provides +3/+3 in stats, making them more than worth the two mana investment required to do so
The card quests for one lore, and 'Chart Your Own Course' gives John Resist +1 and an extra lore to quest for - one for each location you have in play
NIM DEATHMANTLE Emerging from the high-powered Scars of Mirrodin block, Nim Deathmantle plays with one of the most underutilized kinds of reanimation: the defensive Reanimator card