After a particularly rough battle, the pods are out of commission, and Lance took a hard hit in Blue. He’s lost too much blood and none of the humans are viable donors, but Coran or Allura can donate (due to fake alien genetic excuses that sound passable, like their shape shifting can change to the genetic level). As a result Lance gains his marks and a low level of Quintessence manipulation and a nice, healthy, dysphoria due to now being half Altean.

have the worst mixture of 

~~pls protect my son Lance~~ 

and

p l e a s e  m o r e  l a n g s t!#@$#