How could a level 5 Summoner detect a Phase Spider who is on the Ethereal Plane?

Question

One of the Same Game Test encounters for a level 5 character is the Phase Spider. The test was originally written for D&D 3.5e, but I wanted to run it for a character that I am creating for an upcoming campaign, an Unchained Master Summoner.

It's a rather straightforward thing to fight once you know it's there, whether it announces its presence by appearing, attacking, and then disappearing, or if you notice it via a successful Perception roll.

However, is there any way for a level 5 Unchained Master Summoner to at least locate the Spider after is uses its Ethereal Jaunt ability?

Answer 1

See Invisibility

At level 5, the Unchained Summoner would have 2 level 2 spell slots.

See Invisibility is a 2nd level Unchained Summoner spell that says:

You can see any objects or beings that are invisible within your range of vision, as well as any that are ethereal, as if they were normally visible. Such creatures are visible to you as translucent shapes, allowing you easily to discern the difference between visible, invisible, and ethereal creatures.

Therefore, See invisibility would allow a 5th level Unchained Summoner to see the phase spider.