Magical Knights love playing with 3 concepts: Mana, Silencing and Counterspelling. It's a weapon class with a lot of removal and cards that benefit a control play style. In the Basic and Classic set, there are cards that gain their power from unspent Mana, either yours or your opponent's, cards that Silence minions in unusual ways and many spell hate cards, like spell immunity, negative spell damage and reactive countering (not proactive, like Counterspell or Loatheb). On later sets, Magical Knights will gain new counter toys, like discarding from enemy hand, locking enemy hero power and transporting minions into the Netherworld (an alternate "graveyard", minions going there are not considered dead).
Mana Harvester takes advantage of your unspent Mana and makes sure that it won't go in vain. Evocation gives you 3 extra mana, but does not let you ramp up, it only fills spent Mana Crystals. As long as Mortron is on the battlefield, enemy minions have their card text deleted. They are restored once Mortron leaves the battlefield. This does not restore previous buffs, but only the card text.