6.81b tremendously weakened Invoker's lane dominance. Instead of killing or zoning out your opponent in middle lane, focus on winning creep score and deny runes with forge spirit. This build is especially good against Blood Seeker, and Drow.

Map Awareness is very important. When you are free farming safely in mid lane, clear creeps with meteor, pull incoming creep wave away from tower with forge spirit, and destroy tower with alacrity. Mid tower can be defenseless for an entire minute!

At level 10, focus down your targets with forge spirits and cold snap. Meteor and Sun Strike are your next strongest spell. At level 16, you can start using the Tornado, Meteor, Blast, Ice Wall combo.

Do not attempt Refresher orb Combos until level 23 minimum.
Beware of heavy aoe magic heroes. they will blow up the forge spirits in just a couple of seconds.