Essence Channeler

If Essence Channeler has -1/-1 counters on it when it dies, that ability will include those as well. This may result in the recipient of the counters also dying.

Each creature with lifelink dealing combat damage causes a separate life-gaining event. For example, if two creatures you control with lifelink deal combat damage at the same time, Essence Channeler’s second ability will trigger twice. However, if a single creature you control with lifelink deals combat damage to multiple creatures, players, planeswalkers, and/or battles at the same time (perhaps because it has trample or was blocked by more than one creature), the ability will trigger only once.

In a Two-Headed Giant game, life gained by your teammate won’t cause Essence Channeler’s second ability to trigger even though it caused your team’s life total to increase.