Most aggresive enemies stop being aggresive when you have more than twice their level.
Go into the deepest part of the Wilderness and they will appear. BEWARE: THEY ARE LEVEL 131 EACH!
id say power train on like skeletons or black/white knights.
Level 138, i'd highly reccomend Proctect from Melle prayer, as it is multiway combat, it is also a great spot for chinchompas.
Black Dragons are level 227.
the kbd is something over level 500
Ball Sack
In the game Runescape the level black dragon is 144. The black dragons are powerful monsters, an anti-dragon shield, a dragonfire shield, or an antifire potion or even both of them is highly recommended when fighting them.
There aren't that many monsters to attack at your level, but you should try the Black Knights' Fortress which is just North of the Dwarves on the map. Also you could try going to the Fist of Guthix or the Duel Arena near Al Kharid.
in second level of white knights castle his name is not herald hes sitting on the chair in the east side of the castle
I say whenever your prepared, but if your not sure, level 100 will be fine.
ANSWER #1: It is worth it but you have to have level 40 in defence!
King black dragons level one in the wilderness 47