Invigorate is basically always free to cast (and therefore easy to copy with Riku) because you can always give the three life to an allyor give it to a person you are planning on killing with Riku commander damage, since that bypasses life totals anyway
A Tier: Fun, Interesting Designs Qala, Ajani's Pridemate -- It's exciting to see Ajani's Pridemate get a name
However, Mindslaver's salt factor comes from the fact that in commander, there are numerous ways for players to consistently return artifacts from their graveyard to the battlefield
That means its vulnerable to removal spells and often wont draw as many cards as you wish it would
Here are the top blue card draw engines for Commander, perfect for the Philippine MTG market: #1 | Rhystic Study This is the most respected draw engine in Commander
Games were slow, high-curving, and incredibly grindy