Spell maintenance is a feature originating in FIQhack, but which is also present in dNetHack. It allows you to maintain self-buffing spells continuously without needing to recast it every now and then, in exchange for it draining your energy reserves over time (which can potentially be outregenerated if your energy regeneration is fast enough). This energy cost will generally be twice the spell's level (or four times for light and protection) every 5 turns, but can be more with the Amulet or with a failure rate higher than 0%. Spell maintenance can wear off if your energy runs out, you become confused, or at random if your failure rate with the spell is high enough. Unlike normal spellcasting, in FIQhack (but not dNetHack), maintained spells will not drain any hunger over time. It will, however, also not exercise any skill.
These spells can be maintained:
In FIQhack, these new spells can also be maintained: