I had some ideas for tools that modders could use to create interesting effects in the game. 1. Spell effects that trigger when the character levels up a skill. This will allow the modder to create sophisticated effects that do not have to be activated by the player. For example. If this feature existed, the modder could create a skill that caused the player to have a permanent halo effect. This is mostly aesthetic, but more profound changes could be implented, such as a recurring radial template effect that confused diggles. 2. Spell effects that trigger when an item is equipped or removed. This would allow for creative things like a constant halo effect when a crown or sword is equipped, a "curse" effect, like a pair of clown shoes that cause your footsteps to turn into sqeaks and occasionally you trip and hurt yourself. This differs in what currently exists because it allows the modder to create triggered effects that can occur independently of other events. Example: you can create an evil sword that drains the life force of the wielder as he carries it rather than when he hits something with it.
Items that come with enchantments would be really neat. However, if a sword worked as you described, one could just unequip it when not in combat. That would be so incredibly tedious! Please never do such a thing. Regarding the level-up mechanic: I'm trying to understand what you want. I assume that a skill can only grant one new activated skill when it's taken, and you want to give the player an activated skill and a passive spell, like an enchantment. If I'm mistaken and you don't want to give them two things at once, then what's the harm of just making the enchantment an activated ability with no upkeep that they can turn on and off at will? Even if you had the ability to enchant a player with a spell when they took a skill, how would you program a continuous effect that confused Diggles? Is there a mechanism in the game where a spell effect can be continuously cast at targets around you? I can't think of such a thing, and that sounds like a separate request.
You might not want the player to be able to turn the effect on/off. Example: a skill that permanently polymorphed you. You can have DOTs and Buffs with infinite duration.
I understand that, but how does that answer my question? I'm imagining that what Ruigi is talking about is a spell with a template that follows you around wherever you walk, casting confusion on each Diggle in the effect radius. He mentioned a "radial template effect". That doesn't sound like a simple buff or DoT.
DOT in Dredmor just means a spell that is triggered once a turn. It can be any spell - including template spells. For example, if you DOT'd the spell 'Big Dig' you could walk around and have the walls melt around you every turn.
One way to avoid this abuse would be to force the player to pay a big cost up front when the weapon is equipped, and then pay a much smaller upkeep as the weapon is equipped. this would make it difficult to get a benefit from swapping gear like that.
If there were also a trigger upon removal, you could more directly discourage fiddly gear swapping. Related suggestion: items which give a castable spell to the player while equipped. Among other things, this would provide other-than-Gargleblaster mana sinks for non-mage builds.