you probably want those for the bonus/grimoire? A lot of the ones seem to not count. I think the ogres on moon patrols count. The one right inside temple of Crota, and there's a second one sometimes in the room to the left after the spiral staircase from the archer's line entrance. I think there's another one that has a chance to spawn on the way to the world's grave. Another spawns near the end of the shrines of oryx mission. As for Hydras, there's one halfway through the eye of a gatelord mission. Another one is halfway through the black garden mission. The one that spawns at the vex gate on mars patrol should work too.