make em bad ...or good ,but with evil pupils that corrupted their legacy... heheh it 'll be a nice excuse for "evil" cults ..
throw in some radagast - nature - good shamanism cult ,as counterpart in mid-west regions and the soup 's ready for supper
since the "fourth age" is a bit vague, make a nice fan-fiction approach ..no heavy-magic/sorcery just "occult" elements for the fantasy part
ps..maybe (if the map isn't completed,also implement a dwarves' regions in rohan..the "glittering caves"..gifted to gimli by the rohirrim
and an elven "colony" in ithilien led by legolas.. )