By drinking this essence, you have access to an entire planet's worth of mana.
*Just like Jinkyung from Her Summon, you have access to an entire planet's worth of mana, allowing you to do impossible feats. Unlike Jinkyung, rather than having a direct connection to this source, it is instead fused with you, allowing it to grow as you continue using this power. It is not infinite, but it can quickly regenerate after a few seconds.
*Just by being connected to this source, you can casually tank blasts capable of cracking continents, run and react faster than the speed of light, destroy mountains with just a punch, and be immune to the worst poisons and curses. This can be increased through the efforts of training and usage of magic.
*In Her Summon, magic is powered by imagination and mana. With a planet's worth of mana, you can basically warp reality. In the story, Jinkyung was able to create an explosion equal to a nuke with bug spray, heal fatal injuries and regenerate tissue using bandages, used a laser pointer to destroy a distant planet, and created an AT-Field from Neon Genesis Evangelion using a mosquito coil and caused a shockwave that can be seen from outer space. And he was able to do all those things without trying. Though it is easier to use items to achieve these effects. The more powerful, complex, rare, and/or old an item is, the greater the effect it will bring out. A bandage could heal any wounds, but a magical healing potion could resurrect the dead. With training, you would be able to do these things without any aid.
*This power can never be taken away from you.
*Optionally, you can be summoned regularly by a young novice summoner who calls for your aid. It does not have to be the one in Her Summon but in any fantasy world you desire.