Deliah, Puppeteered Protector

When Deliah deals combat damage, it phases out.
Whenever Deliah phases in, if you don't control
an artifact named Obsidian Greatsword, create Obsidian Greatsword, a legendary black
Equipment artifact token with "Equipped
creature gets +2/+0 and has Lifelink,"
"Whenever equipped creature attacks, you may
pay {x}. If you do, equipped creature gains
+X/+0 until end of turn" and equip {3}.
Otherwise, each opponent loses 1 life and you
gain 1 life.