Blister

The Blister is a non-moving Hard Mode enemy that 'grows' in the Crimson. They can grow either aboveground or underground in the Crimson, though they spawn more frequently in the Underground Crimson. if you get to close (about 7 blocks) they rupture and deal 50 damage to anything caught within it's radius. If you manage to kill it before it explodes, it will drop Pus and 2 Silver Coins. it can also spawn Pus Flies.

Stats

 * 25
 * 50 damage (explosion)

Drops

 * 2-8 Pus (100%-if killed before it explodes)
 * 2 (100%-if killed before it explodes)

Credits
Credit for this sprite and idea goes to J-50N

His profile can be viewed here: http://www.terrariaonline.com/members/j-50n.133318/