This move can be used when the shield is charged. It is cancelled from SAED, like elemental roundslash and AED. Currently the input for Savage Axe Slash is not known.
The attack itself does not directly consume any phials.
After using SAS, you will receive the Chainsaw buff. This shows as a red axe icon next to your shield and sword icons. You do not need to hit a monster to gain the buff. While you have this buff, all Axe attacks will deal additional small hits as they pass through a monster. These additional hits are physical attacks that are affected by hitzones. Important: these additional hits all consume sharpness.
The buff lasts until the moment you have 0 phials. While the buff is active for Impact Phial charge blades, you lose 1 phial every 12 seconds (Elemental phial weapons are supposed to have a longer buff but it’s currently unknown how long). This timer does not stop while in sword mode. This timer is reset whenever you expend a phial attacking.
You can keep refilling phials in sword mode to extend the buff. Of course, using SAED will immediately end the buff.
This clip shows a sword mode attack (morph to sword) dealing additional hits. It’s not known whether the chainsaw buff affects all sword moves or only this one.
SAS has a guard point at the beginning of the attack. This gives Axe mode the ability to guard point. You will not gain the chainsaw buff if hit during the guard point.
SAS can combo into the following moves. Notably, you can’t SAS into SAED or ED2. “Rushing Element Discharge I” is not a new move, it’s just ED1 but you move forward more.