Blood of the enemy on fire mage

So I´ve been checking out the site, looking for the builds used by the top players and constructed a BiS for said builds.
Some things confuse me however, and that would be how do I utilize blood of the enemy as a fire mage? When do I use it? Why is it better than memory of lucid dreams?
Thanks in advance.
-A very confused fire mage

You would use it right before combustion.

I could see being able to do silly things with it to get huge parses. I’m not sure if it would be categorically “better” than memory of lucid dreams though.

What would these silly things be?
And could that be the reason it´s the “best” essence according to the guide?

I mean, it gives you crit damage for almost half of combustion, which is pretty huge. If you can use it well it has good potential. The memory of lucid dreams combo is probably easier to deal with and does just as much damage - looking at the guide i see both of them scored pretty close to the same.