Air Elemental Familiar

Innate Spellcasting. The air elemental familiar's innate spellcasting ability is Charisma (spell save DC 10, +2 to hit with spell attacks). It can innately cast the following spells, requiring no material components:

At will: gust

1/day: feather fall, fog cloud

Air Form. The elemental can enter a hostile creature's space and stop there. It can move through a space as narrow as 1 inch wide without squeezing.  Using an action, the elemental may turn invisible but take no other actions or move while invisible.  Other creatures, other than the master, have disadvantage on Wisdom (Perception) checks to see the elemental when the elemental is not holding any gases.

Gas Absorption/Filtration. The elemental can absorb and compartmentalize various gases in its body such as farts or a Brass Dragon's Sleep Breath.  When doing so, the elemental can use an action to mix any gases it is holding or spend 1 minute to filter the gases to be safe for breathing.

Gas Mask. The elemental can use an action to form itself around a creature's head to filter poisonous for the creature to make it breathable.  If the elemental is holding gases within its body, the elemental may also force a creature to breathe any gas it may be holding.

Change Form.  The elemental can change its element during a short or long rest.  For 1 hour the elemental because a small ball of elemental energy that appears to expand and collapse in on itself as it transforms.  While transforming the elemental has no use of its senses but can communicate with its master and can be disrupted during this process.  

Familiar. The elemental can serve another creature as a familiar, forming a telepathic bond with its willing master, provided that the master is at least a 3rd-level spellcaster. While the two are bonded, the master can sense what the elemental senses as long as they are within 200 feet of each other. If its master causes it physical harm, the elemental will end its service as a familiar, breaking the telepathic bond.

Slam. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 3) bludgeoning damage.