I've been playing this game for a long time but I cannot recall if there has ever been an iconic group of monsters of neutral good (or for that matter chaotic good or true neutral) alignment native to the other planes in the way that other alignments have their iconic creatures (5e names used - they have had other aliases):
\begin{array}{c|c c c} & \text{Lawful} & \text{Neutral} & \text{Chaotic} \\ \hline \text{Good} & \text{Angels} & ? & ? \\ \text{Neutral} & \text{Modrons} & ? & \text{Slaadi} \\ \text{Evil} & \text{Devils} & \text{Yugoloths} & \text{Demons} \end{array}
Can anyone fill in the blanks?