Mars

Use Gods Rebuke to secure ranged creep last hits and harass the opponents at the same time.

You often want to set up a Spear of Mars by God's Rebuking first.

Arena of Blood destroys trees in huge AoE which can be useful against certain heroes.

Dont rush spearing an enemy during Arena of Blood. It's often times better to rebuke and spear with delay.

You can protect your allies from ranged attacks by placing Arena of Blood or using Bulwark.

Don't over rotate. Focus on getting Blink Dagger or Eul's Scepter timely.

Make use of the Blink Dagger immediately before opponents are able to scout it.

Pick up Aghanims Shard after Blink and BKB to have even more damage and control with Spear of Mars.

Attack modifying and proc items work with God's Rebuke. You can pick up Satanic in the late game for example.

Avoid playing close to trees against Spear of Mars. Cut some with Quelling Blade and Tangoes.

Mars takes reduced damage from front and sides once he levels up Bulwark. Hit him from the back if possible.

No range attacks can hit inside or outside of the Arena of Blood.

Arena of Blood destroys all the trees around it.

Be aware of Mars's Blink Dagger timing. Look to cancel his Dagger in the fights.

Avoid fighting in choke spots and clumping up against Blink Dagger into Arena of Blood combo.

Black King Bar allows you to move in and out of Arena of Blood.

Break effects remove Bulwark and Mars becomes significantly weaker.