? Question: Certain creatures have Power equal to the number of a certain type of monster in play (e.g., "Swarm of Rats"). If they are the only such cards of their type in play, is their power 0 or 1? --Answer--

? Question: "Swarm of Rats" has power equal to the number of Rat cards the owner has in play. Do the 1/1 Rat tokens summoned by the Lab Rats card add to the power of the Swarm? --Answer--

? Question: "Rats of Rath" have a special ability that allows the owner to tap 1 Black in order to "Destroy target artifact, creature, or land you control." Why would anyone want to destroy a permanent that they control? This does not sound like a very useful ability. --Answer--

? Question: When the rat tokens summoned by the "Lab Rats" sorcery are slain, do they count as creatures in their owners graveyard for purposes of spells affected by this? (e.g., "Soulshriek", where "Target creature you control gets +*/+0 until end of turn, where * is equal to the number of creatures in your graveyard"). --Answer--

? Question: "Crypt Rats" give their owner the ability to "tap X: Crypt Rats deals X damage to each creature and player." Can this ability be used as often as desired? Can it be used defensively during another players turn? Can it be used even if the "Crypt Rats" card is tapped? Presumably, the Crypt Rats themselves are immune to the damage caused by this ability? --Answer--

? Question: Will the special ability of "Rabid Rats" ("tap: Target blocking creatures gets -1/-1 until the end of the turn") slay a target creature whose toughness is reduced to 0? --Answer--