would Yahenni's +1/+1 counter ability trigger when you sac it? i mean if it doesn't, Yahenni doesn't really get big from sacrificing creatures to him, just indestructible.

Under_torment You sac to make him indestructible, then use Bontu's Last Reckoning, he'll get counters from your opponent's creatures that die from it. Bone Picker and Gifted Aetherborn have deathtouch, so when they block something or get blocked, Yahenni will get a counter since your opponent's creature will usually die from this.

fair enough, i realized this after it had been posted, its a brilliant deck, and i have tried it out myself, though i have to say, not too many opponents were happy with me after, lol

A second question though, why 4 copies of Yahenni, Undying Partisan? I did find a game or two with a copy or two in my hand while he was out on the battlefield.

Under_torment I put 4 copies just to always have a sac outlet, he seems to be the best outlet because he can do it at instant speed if needed.