Legacy Blue Slime
From TMW: rEvolt
May mutate 1 attribute up to 20%.
Looter, summons slaves
Blue Slimes are very common in the caves of Nivalis. It looks like they are accompanied by two smaller blue slimes, but one of them is directly connected to the Blue Slime itself and therefore not really a separate monster, while the other one is another mob called a Slime Blast. It is THESE little critters that you need to worry about, when attacking a Blue Slime!
Many people don't understand the behavior of Blue Slimes, which can cause problems fighting them or monsters in the same area. Blue Slimes themselves are peaceful monsters that won't attack you unless you attack them, but they endlessly summon aggressive Slime Blasts that will rush you and self destruct. Since self destruct uses splash damage, this harms not only the player targetted by the Slime Blasts, but also other players nearby.
Another problem is that the damage caused by this self-destructing behaviour isn't shown as a number on the battle screen, unlike any other monster, which shows you how much damage it is receiving, or has received. It is hidden, so you often don't realize you have been hurt and maybe even die by surprise. This can be avoided by immediately killing the Slime Blast as it appears, but there is another problem: when they spawn while other mobs are around it, it is hard to immediately target and kill them, due to their small size and fast speed. Adding them to the priority attack list can help (use your right-click options on the monster in the game, and you will see this option). When you kill the Blue Slime, its slave, Slime Blast, will die too, but as long as the Blue Slime lives, it will summon another Slime Blast a few seconds after you killed the previous one. This behavior often makes Blue Slimes overestimated, but they aren't too strong. Use a strategy when fighting them.
Furthermore, Blue Slimes are looters. They collect other drops. Since they are not often targetted due to the behavior of their partners, who knows what they could hold.