Here is a basic Mock-up I made in my spare time. Everyone let me know what you think! I am open to edits. As is, I would say this is a pretty tough 1/2 Cr, I might end up taking a hit die from it.

[hider=Gallion]Gallion
Medium beast, unaligned
Armor Class 13
Hit Points 18 (4d8)
Speed 35 ft., fly 30 ft.
STR
12 (+1)

 
DEX
16 (+3)

 
CON
10 (+0)

 
INT
3 (-4)

 
WIS
10 (+0)

 
CHA
8 (-1)

Skills Athletics +3, Stealth +7
Senses darkvision 60 ft., passive Perception 10
Languages —
Challenge 1/2 (100 XP)
Keen Smell. The Gallion has advantage on Wisdom (Perception) checks that rely on smell.
Pounce. If the Gallion moves at least 20 ft. straight toward a creature and then hits it with a claw attack on the same turn, that target must succeed on a DC 13 Strength saving throw or be knocked prone. If the target is prone, the Gallion can make one bite attack against it as a bonus action.
Actions
Bite. Bite: +5 to hit, reach 5 ft., one target. Hit: 7 (1d8 + 3) piercing damage.
Claws. Claw Attack: [+5] to hit, reach 5 ft., one target. Hit: 6 (1d6+3) slashing damage.[/hider]