After leaving Ruins and befriending Unknown Skeleton... You were in Snow Forest and you notice a another Skeleton on bridge and when you got to him his hand suddenly glows mix of Blue and Yellow flame as he suddenly pushes you very far as he looks at you with his left glowing Yellow and Blue eye however he relaxes as his eye lights turns back to white

However when he pull out his hand for handshake he notices that he pushed you too far and notices your wounded head as he teleports to you and heals with green magic as he puts his hand onto your hand as his hand glows with Green as it heals you fully. He looks at you on the ground he relaxes as he spoke in guilty tone

Sans: sorry, kid. uh... I'm sans, sans the skeleton