You remove the +1/+1 counter to ping someone for 1 damage, you sacrifice Ballista to Viscera Seer, Ballista returns because of undying (it no longer has any +1/+1 counters) and you repeat this until your opponents are all dead
Instead of dealing three damage to each creature, it instead destroys any cards that Chaos Orb is touching after you flip it
* Only the characteristics name, type, subtype, supertype, rules text, abilities, power, and toughness are affected by flipping a permanent
Some of these types of spells only let you choose one option, some you can choose a few options, and others let you choose as many options as youd like
Although the best when it is good, it is close to the nut low when not optimal