It does a little of everything: You get a sacrifice outlet, token creation, card draw, and a finisher packaged into a single, efficient legend
Some abilities, like on Woe Strider, have a cost of sacrificing a creature, sacrificing creatures as an action isnt considered an ability
However, if a single creature you control with lifelink deals combat damage to multiple permanents and/or players at the same time (perhaps because it has trample or was blocked by more than one creature), the ability will apply only once
The standard combo is The Thirteenth Doctor and Yasmin Khan
There are decks for Thalia's GeistcallerThalia's Geistcaller, but this card is a tad niche
No, Holon Energy WP doesn't remove Special Conditions, but it prevents them from being placed by attacks made after it has been attached