What it does
Cleave gives a spell two ways to be cast. When you cast it, you can pay the cleave cost (an alternative cost) to ignore the words printed in brackets on the card. If you pay the normal cost, the bracketed text stays and the spell has a more limited effect.
The nuance people miss: cleave isn't a "better" mode you always want—removing the bracketed text sometimes makes the spell stronger but not always, and if removing those words leaves the spell with no legal targets, you can't cast it that way. Also, cleave is chosen as you cast the spell and locks in the cost; you can't switch later. The bracketed text is fully gone for all purposes when cleaved, including copy effects.
In Commander, cleave's flexibility shines: cards like Bloodthirsty Adversary aren't cleave, but Crippling Fear's cleaved mode wipes broader boards, letting you scale a spell to the table size and your needs.











