How small can I make a character, mostly permanently, at 18th level?

Druids can wild shape once and become diminutive for (functionally) the whole day.

Other than that, how small can a character get – either permanently or with a few rounds once per day – on a regular basis?

Assume that the character in question has the ability to cast both divine and arcane spells of up to 9th level.

Costly material components should be avoided, but expensive magic items are a-okay; this character ideally wants to be fine 24/7.

For the purposes of this question, assume that Wish/Miracle won’t work (ie., that the GM ruled that such a request is highly likely to trigger the “literal but undesirable fulfillment” clause of Wish, and that the divine power behind Miracle will simply say “no”).

The /etc/issue file gets cut all the way through the 18th line

I have bought an SSD to replace my old HDD to get my laptop(lenovo thinkpad x220) faster, and made up a fresh installation of Arch Linux with an i3wm and no dm(tty only). I have had a nice ASCII art on my HDD and wanted to make the same one on an SSD. Though the /etc/issue file is the same as I had, the file gets cut on 18th line. I wonder if someone knows what is the boot process and what can give such behavior. Wanted to mention that TTY doesn’t display some unicode chars, like ░▒▓.