Friday, 17 August 2007

Summoning veils and blood debts

I wrote a little while ago about various strategies for play-balancing monster summoning, in an article Summoning the Borg. While I haven't come up with an ultimate solution, I'm going with a timer based solution for the moment, where the summoner has a short time-out and the newly summoned monsters have a longer timeout, before they can cast another summoning spell. Called 'summoning veil', this prevents the monster from penetrating through the astral plane to summon allies until it recovers.

This summoning veil also benefits you as a summoner. Summoned monsters can escape through the astral plane, unless they are blocked by the summoning veil. So monsters that you summon will stay in this existance until the veil is lifted.

Or at least that's the in-game explaination. Because, of course, the summoning shoe is on the other foot. I've added player based summoning spells, and I need to balance those as well.

Luckily, I can artitarily prevented player-summoned monsters from summoning again without feeling too guilty, which means that the same exponential growth patterns that I discussed in the previous article don't apply. By adding a timer, I can prevent a player casting a summoning spell, resting to recover mana, and then casting another summoning spell.

However, I've also allowed plenty of spells to recover mana much faster than that. So I need another balancing strategy. A lot of Angband variants reduce the maximum mana that a player with summoned monsters is allowed, and this works well. However, it'll require implementing link lists across monsters, or reference counting or something equally fragile and prone to breakage. It also cuts down on a precious resource (mana) that magic using players desparately need - probably a bit too much.

Conceptually, I can add something similar, and perhaps more interesting, by not reducing the maximum mana, but by giving the player an incentive to keep their mana high, or rapidly incur increasing risk. I call this 'summoning debt'.

If a player summoned monster dies while under player control, the player will incur a summoning debt equal to the power level of the monster. Initially, this is paid out from mana. However, if the player has insufficient mana to cover the debt, they will pay out it out in blood. The blood debt is higher than the mana debt (1d3 hit points for every mana point), and can result in the player dying, if they are too far in debt to cover the costs.

This 'summoning debt' gives a player a big incentive to treat their summons well. If they can keep their minions alive (such as by using wands of haste monsters and thrown healing potions), the player can freely use their mana for other spells or summons. However, if things go wrong, they go wrong fast.

And that's what Angband is all about.

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