Harbinger of the Barbed Saber Creature - Human Assassin Deathtouch Carnage — Whenever Harbinger of the Barbed Saber deals comabt damage to a player, that player loses X life, where X is the number of creatures that died this turn. 1/4
Butchers’ Wisdom Sorcery Carnage — You draw X cards and lose X life, where X is the number of creatures that died this turn.
Decree of the Barbed Saber Instant Carnage — Decree of the Barbed Saber deals X damage to any target, where X is the number of creatures that died this turn. Draw a card.
Tak, Head of the Barbed Sable Legendary Creature - Human Warlock First strike Carnage — At the beginning of your end step, return target creature card with converted mana cost X or less from your graveyard to the battlefield, where X is the number of creatures that died this turn. 4/3
The Barbed Saber Legendary Artifact - Equipment Carnage — Equipped creature gets +2/+2 for each creature that died this turn. Sacrifice a creature: Equipped creature gains first strike and hexproof until end of turn. Equip
"It's not difficult to make Magic players feel smart." - Mark Rosewater
Furthermore, I consider that Carthage must be destroyed.
Lochlin's Master Blueprint Legendary Artifact You may cast artifacts from your graveyard. If Lochlin’s Master Blueprint is calibrated, other calibrated artifacts you control have indestructible. Calibrate (Put a calibration counter on this artifact, it is now considered calibrated.)
Updated: Added blue. Ideally they would all either be replacement effects or additional effects. But it seemed like it would be too wordy for the ones you use on your own creatures. Additionally, the overkill numbers might work better all at the same number, but your initial challenge of 7 was really high for some of these effects. And I would've like to have these at uncommon, but the effects ramp up too much with higher numbers. Oh and having them all be instant or sorcery didn't feel right, so I mixed them up as much as possible, the green one should maybe/probably be a sorcery.