Ascend

Look up, start the ability, and swim toward the light. If the rock is too thick, you are pushed back down and the ability was not spent in a useful way. Cave roofs, shrine floors and the wooden decks of ruins are the usual successes. The underside of a sky island sometimes works when you are already gliding close to it. Stand on solid ground before you start. You cannot begin the swim from midair.

A chest, a person or a monster standing on the exit blocks it. You either fail or pop out beside them already in the fight. Clear the exit, or accept that you are coming up in front of an enemy and have a weapon ready. During the swim you are not taking hits. The danger is the first second after you emerge.

Very thick stone, metal grating in some shrines, and ceilings the puzzle has sealed will reject you. Ascend also fails when the space above is another solid mass with no room to stand. If a cave has a marked exit, that hole is still the reliable door. The ability is the shortcut when you can see a thinner lid, not a promise that every roof is a door.

Use it under a Flux Construct that has become a flat sheet, under a Hinox that is down if you want the eye faster, and anywhere a shrine wants you to appear on the next floor. Do not use it into a room you have not lit. A brightbloom thrown up first, when the hole already exists, tells you what is waiting. Coming up blind into a Horriblin ceiling is a bad surprise.