[MENTION=10148]JEB[/MENTION] thanks, good to see I'm on the right track with 2e to 5e monster conversion. Here's whati came up with for the Astral Searcher...
Astral Searcher
Medium aberration, Unaligned
AC 10
Hit Points 10 (2d8 HD)
Speed fly 40 ft
Senses darkvision 60 ft, passive perception 10
Languages none (see Possession)
Challenge 1/2 (100 XP)
STR 6 (-2), DEX 13 (+1), CON 10 (+0), INT 1 (-5), WIS 10 (+0), CHA 14 (+2)
Incorporeal: The astral searcher is resistant to damage from non-magical weapons, except those wielded on the Astral Plane, made of astral driftmetal, or a githyanki's silver sword. In addition, the searcher can move thru objects and people when not on the Astral Plane.
Possession: If the astral searcher reduces a creature to 0 HP, they fall comatose and the following turn the astral searcher enters their body, possessing the victim and gaining their stats (but not their personality). Speech, skills, spells, and special abilities at first aren't possible, but gradually become available as the searcher adapts to its new body. In most cases the victim is now dying, but in rare cases it may take several days for the victim's psyche to be destroyed (at the DM's discretion). During this time it is possible to save the victim by exorcising the astral searcher with greater restoration, heal, banishment, or wish. It is also conjectured astral projection could work. The victim will remember little of their ordeal.
ACTIONS
Melee Attack - Psychic Claw: +4 to hit (5' range; one creature; this attack ignores physical armor and shields). Hit: 7 (1d8+2) psychic damage and target must make a DC 12 Charisma saving throw. Failed Save: Loses a precious memory, and along with it a skill proficient and a spell slot (if any) until their next short rest.
The bane of travelers to the Astral Plane, astral searchers are mindless shells created by intense emotions - usually anguish - of travelers from the Prime Material Plane. They appear as vaguely humanoid silvery-blue mist. Violent death, combat, and incredibly destructive spells on the Astral Plane create astral searchers. These beings wrongly believe confusion, fear, horror, a rage under which they are created is the natural state of things. Congregating around astral conduits, they attempt to slip into either the Prime or the outer Planes in order to take a body. In some cases a searcher adapts so well that they remain hidden within a community for a long time before being exposed. Rarely, a searcher in the Astral finds peace in its tortured existence, devoting itself to protecting astral conduits; such searchers don't appear to hunger for physical form like others of their kind and are known as "astral guardians" by planewalkers.