These cards just sacrifice permanents, while some sacrifice payoffs are outlets as well
Another infinite combo revolves around sacrificing Gravecrawler to Phyrexian Altar and pinging an opponent with Diregraf Captain to net you the mana needed to cast Gravecrawler from your graveyard again
Table of Contents show How Does Incubate Work
A creature's mana value is determined solely by the mana symbols printed in its upper right corner (unless that creature is the back face of a double-faced card, is a melded permanent, or is copying something else
Its very easy to hit something with Bear Down, and in the case of this card even hitting a token of some kind is acceptable, because you dont use up an entire card to do it, since later in the game you get an efficient creature that is hard to block
I pass the turn, planning to Abrade my opponents Goblin Rabblemaster on their main phase, to give me more time to find a creature for Sneak Attack