Tap Gilded Lotus for ({U} magic symbol) ({U} magic symbol) ({U} magic symbol) and Khalni Gem for ({R} magic symbol) ({R} magic symbol) .
Pay this mana to activate Nin, the Pain Artist's ability targeting Chasm Skulker.
Chasm Skulker gets 3 damage marked on it and goes to 1 toughness.
You draw 3 cards from Nin, the Pain Artist and Chasm Skulker gets 3 +1/+1 counters placed on it, making its toughness go back up to 7 with 3 damage marked on it for a net of 4.
Discard the three cards you drew from Nin, the Pain Artist to untap Gilded Lotus, Khalni Gem, and Nin, the Pain Artist.