The only maps I probably wouldn't take Fealty Unto Death would be Battlefield and Mines, otherwise i'd say it's the go to ability for everything else. Plus with Fealty you'll never need Mana Thirst because you'll be full mana the whole game. At 13, I'm finding so many more uses out of Spell Shield which I find to be underrated. The 30 sec cooldown is brutal, but 3 seconds of 50% dmg reduction to a zeratul/nova gank, kael flamestrike/pyro, jaina, butcher's furnace, etc...this can be a...

I'm not quite sure why you would list Block as being useful against Tychus. His auto attacks will eat your block charges in less than a second and nobody builds him as a basic damage hero.

Thanks, I'll likely expand on it in the future as well. Be sure to check out the video of this build on my YouTube video above too :)