Ancients

Every act opens on one of them: the first node of the map is the ancient node, and the visit heals all your missing HP (80% of it from Ascension 2, Weary Traveler), plays a short exchange that changes with the character you climb as, and lays out a choice of relics built from that ancient's own pools, of which you keep one.

Which ancient you meet depends on the act. Neow waits at the start of Overgrowth and Underdocks once her epoch is granted, which happens the moment your first run ends; before that the start node is an ordinary fight. Hive rolls between Pael, Tezcatara and, once unlocked, Orobas; Glory between Nonupeipe, Tanx and Vakuu. Darv is shared: at run start the game deals him at random to Act 2, Act 3 or neither, and in an act that receives him he competes with that act's own ancients for the node. The Architect is not a node at all but the final confrontation after the last boss.