Purple Haze	A smokey mist that he secretes if you get near him, the only effect is has on you is slowness: Its tough to avoid this since you'll be too close to react fast enough, so you'll just have to grin and bear it.
Heavy Swing	Another close-range attack is a full body swipe with his wooden appendage: It does a fair amount of damage and hard to avoid, so its best not to get too close to him.
Poison Mist	Armstrong rears his head back and then spews out a greenish poison mist: Simply stand to the side and continue hacking, it'll go harmlessly by you.
Needle Storm	He'll rear back his wooden appendage before wailing on you with razor-sharp needles: As before, simply stand off to the side as you see him rear, and continue hacking away.
Cannon Blast	His final attack is a huge cannon that can take a nice heart out of your life: He's quick to the draw on this weapon, so when you see his cannon moving, run! He'll only shoot where you last were.

Later Cycles: Along with getting stronger and faster, his main cannon attack sports a Stop condition in cycle 2. It further adds a Curse effect to your character in cycle 3. The Skeleton mages should be quite abundant in the later cycles, but as long as you keep moving their spells won't harm you. Unfortunately for magic users, it may be harder to pull off a triple-fused spell during cycle 3.