There were no thoughts running through Lex's mind, but he wasn't dead yet. He could still feel pain. He could feel his body - what was left of it - protesting aggressively against his every action, or rather his only action.
His right hand, repeatedly squeezing and relaxing, forcing his heart to pump. Things had not gone according to plan. He placed the egg shell on his heart expecting to fuse with it when his Rebirth by fire ability kicked in. But the ability wasn't kicking in.
No wonder Phoenix's were on the verge of extinction - their ultimate ability, which triggered upon entering a near death state, came with performance issues.
Thus, even with his mind shrouded in darkness, and even with all his thoughts disappearing, Lex could feel the pain in his body. Pain - it was so easy to ignore when he had a goal, a purpose, and some energy to pursue those goals. But when all he felt was pain, with no mind to understand context, it was not so easy.
