Metroid Prime kinda looks like a heart when it's curled up, hanging in the center of a giant teratoma cave full of giant teeth and pulsating floor. Its theme has the constant beating of heart.
https://www.youtube.com/watch?v=6_BUofQCJLAHere's the scene Kiara missed by not 100%ing all items and scans, if you were curious but forgot to check for yourself.
https://www.youtube.com/watch?v=y_mo1bMPC5gWell, it's the original GameCube version of the scene. The remaster somehow even fucks up the darkness of an animation and the
eye is barely visible.
MP rips the Phazon Suit off of Samus and fuses with it to become Dark Samus, who you fight a bunch in Metroid Prime 2 and 3.