This is the second iteration of this question about the first iteration of this feat (I have now made a third iteration)
I have now added in some of the suggestions given by linksassin such as simplifying it to just one type of rune and adding a material cost. I have not added in limited duration or limited number because it is intended to allow the player to make a consumable similar to spell-scrolls or potions. if they intend to make them during extended downtime then thats fine, its the same as making spell scrolls or buying potions during downtime.
Rune Caster
Prerequisites: ability to cast at least one spell of 1st level or higher
When you take this feat you can imbue your spells into a rune by casting the spell as a rune, this means that you must have the object you want to put the rune on within reach for the whole duration of the casting as well as any tools required to make the rune. The casting time is also affected.
Casting
When casting a rune you add 1 hour to the casting time and 20gp per spell level stored on top of the normal components of the spell.
Triggers
When making a rune you may customise the trigger conditions from the following
list:
Touch
Command word spoken
… by [specify creature(s)]
… with [specify body part]
When defining creatures that can activate the rune you may be as specific or general as you want. The DM interpretes the designated creatures as your character would have interpreted them when you made the rune.
Ranges
When you store a spell in a rune the following rules change the range:
A range of touch becomes a range of self
When a range is listed and a target the person who activates the rune designates the target
When a range is used with an aoe the origin is automatically wherever the rune is.
Activating a rune
When a rune is activated the spell is released acting as if it had just been cast without requiring any components. The rune then disappears leaving no trace of its presence. To activate a rune you must complete the trigger, this means speaking any command words and physically touching the rune each if applicable.
I want to know specifically is it to powerful/ not powerful enough and if so what would be a reasonable way of correcting the issue.
Best Answer
This is a little too powerful
When it comes to 5th edition tactics, spreading the role of Concentration around is very effective as it allows the high Constitution characters to concentrate on their own enhancement spells like enhance ability, haste, or polymorph. This also opens up the spellcaster's Concentration for other spells (usually less tactically important ones such as entangle or cloud of daggers).
Your feat makes accomplishing this virtually trivial. You simply pack a rune with the enhancement spell for 20 gp (a relatively small amount) and the fighter/barbarian/paladin has its own Concentration spell. This is even more powerful than spell scrolls (which linkassin's answer tackles the relative monetary and time costs of) since the character need not even possess the correct spell list to gain access to the spell.
Stockpiling
This also allows the stockpiling of runes for a dangerous dungeon throwing out encounter balance. Scribing spell scrolls takes significant downtime, but a spellcaster could convert their entire set of spell slots into runes in a day at lower levels. This means that they have a full set of additional spells to use for whatever difficult challenge presented itself.
Wording
There are a few instances in your homebrew where the wording doesn't quite align with the styles that Wizards of the Coast seems to adhere to. Here is a revision I put together in an attempt to remedy this. It is by no means 100% supported, but based on observations I've made in reading through the books (probably too many times):
Note that I removed the wording about choosing targets since it is redundant as the creature casting the spell always chooses the targets. Additionally, the section on having the GM interpret the trigger "as the character would" is largely confusing and if the GM is actively trying to use wording to adjust the usefulness of the feat, there are probably other problems at the table. The rest of the changes are mostly to allow it to read in plain English with some small word-choice decisions based on other similar examples in the official content.