"Your fragile bones are like toothpicks to me."; "You little weasel will not live to see another day."; "I'm just a messenger of what's yet to come."; "HRAAAAAAAAAAAAAAAARRRR!"; "I'm taking you down with me!".
Hellspawns are fast. They are usually found in groups with other hellspawns, and maybe some other creatures
Hunting Hellspawns at lower levels requires a small group of players to make a hunt profitable.
Also if you're a knight blocking more than one always check your Hit Points because if you are facing two or more they can kill you in one combo, even on a decently high level knight.
Mages should keep at a distance as Hellspawns hit rather hard with melee and are pretty fast. It's fairly easy to solo them at level 100, but be careful not to face more than one as they have a strong melee attack. Trying to outrun them while using Ice Strike could help reduce waste. Summoning Demon Skeletons can be useful to Druids sioing a blocker; Hellspawns rarely retarget and die much quicker with the combined attack of a Hailstorm Rod, Ice Strike, the Demon Skeletons and the Knight's attack. Knight's can get a reasonable amount of exp meleeing the Hellspawn. This method can reduce mana costs.
Knights hunting in a group of 2-3+ of knights is a good option since they hit pretty hard, hunting in groups with a Druid and other shooters is also a very good option. They have good Defense but they aren't that strong against Physical Damage, so a good tactic is to lure 2-8 hellspawns then using Fierce Berserk while a Druid is healing you. The hits will be pretty good.