A land that becomes a creature because of the first mode will retain any other supertypes, card types, subtypes, and abilities it had.

If you choose both modes, the effects happen in the listed order. The lands will become 1/1 creatures in time to deal damage to the target of the second mode.

Once you've chosen both modes for the spell, it doesn't matter whether you continue to control a commander. This is true even if you somehow no longer control a commander as you finish casting the spell.

Even though the card is named after a specific character, controlling any commander will satisfy its condition.

If some but not all of the targets become illegal, Kamahl's Will will resolve but have no effect on illegal targets. If the target of the second mode becomes illegal, no damage will be dealt.

Once you've announced that you're casting a spell, players can't take any actions until you've finished doing so. Notably, opponents can't try to remove your commander to change how many modes you may choose.

The commander you control doesn't have to be your commander.

There's no extra bonus if you control more than one commander.