Creatures with Deathtouch always destroy a blocking creature.
Creatures with Lifelink allow to gain life equal to the damage they deal-their power.
Creatures with flying cannot be blocked by creatures without flying. Flying is most often found on blue creatures, and least often found on green creatures. Some green creatures, however, have Reach, which enables them to block creatures with flying.
Its frustrating to assemble a great mono green deck and then encounter a deck full of flying creatures. You site there and watch your opponent attack and your green creatures cannot block because they do not have flying. Somberwald Spider is one of a few creatures that can block, using the ability Reach. It also has the Morbid ability.
