Oloro, Ageless Ascetic

• WWizards of the Coast2013-10-17
  Official Ruling
  In a Two-Headed Giant game, life gained by your teammate won't cause the ability to trigger, even though it causes your team's life total to increase.
• WWizards of the Coast2013-10-17
  Official Ruling
  In some unusual cases, you can gain life even though your life total actually decreases. For example, if you are being attacked by two 3/3 creatures and you block one with a 2/2 creature with lifelink, your life total will decrease by 1 even though you've gained 2 life. Oloro's second ability would trigger.
• WWizards of the Coast2013-10-17
  Official Ruling
  If Oloro is your commander, its last ability will trigger at the beginning of the upkeep step on your first turn.
• WWizards of the Coast2013-10-17
  Official Ruling
  If two creatures you control with lifelink deal combat damage at the same time, Oloro's ability will trigger twice. However, if a single creature with lifelink deals combat damage to multiple creatures, players, and/or planeswalkers at the same time (perhaps because it has trample or was blocked by more than one creature), the ability will trigger only once.
• WWizards of the Coast2013-10-17
  Official Ruling
  You decide whether to pay as the second ability resolves. If you do, you'll draw a card and each opponent will lose 1 life.
• WWizards of the Coast2013-10-17
  Official Ruling
  Oloro's first ability works only if Oloro is on the battlefield.
• WWizards of the Coast2013-10-17
  Official Ruling
  Oloro's second ability triggers just once for each life-gaining event, no matter how much life is gained.

Rulings via Scryfall