You can indeed. Theurgy has capacities beyond standard gifts, see p62.
Theurgy is much more powerful than low magic. Things it creates
and enchantments it lays will persist indefinitely unless otherwise
indicated. It can reach beyond the boundaries of a single realm and
even plumb the depths of Uncreated Night. It can create new forms
of life and alter old ones, bringing forth new races of creatures that
breed true. There seems to be no limit to the power that theurgy is
theoretically capable of accomplishing.
A scene lasts fifteen minutes, see p25.
Some gifts require that Eﬀort be committed for longer periods,
such as for a scene, or even for a full day. A scene simply means for
however long the current event is happening. A fght is usually one
scene, as is an infltration of a house, a debate at court, the pursuit of
a ﬂeeing enemy, or other such action. Most scenes last no more than
ffteen minutes, though longer ones exist at the GM’s discretion. At
the scene’s end all Eﬀort committed for that scene is returned. Eﬀort
committed for a scene or for a day cannot be reclaimed early.
So at level 1 you can summon 1d6, 3.5 average skeletons per effort. You regen every 15 minutes and have 2 effort, so in an hour you can summon 28, in a day 672 in a day. Here's a table saying how many you can summon by level, ignoring any need for sleep or time to summon them (such things are essentially rounding errors)
That said, there are some limitations over the standard gift.
- You can't make 2HD per level minions. Even a vast number of undead has weaknesses compared to one very strong minion.
- You need to find appropriate parts. The gift can summon them from afar.
- It's not an effective combat gift. You may need the undead now, and this gift cannot do that.
- A necromancer who requires 36960 corpses to make a large army is more suspicious than a necromancer who just requires a wave of their hands.
- It requires binding sorcery, not death, so you don't have access to the other deathly buffs.
The creator commented on this.
It depends on what you're using it for. If you're trying to make an undead army, the RoPB is nominally better if you actually have access to an army's worth of corpses, which is a non-trivial complication. It's not something you're ever going to be able to use without substantial preparation.
If you're trying to call up a swarm of undead meat shields or extra bony hands to do potentially lethal work, then APCB is better, because it only takes an action, doesn't require lengthy Effort commitment, and requires no preparation to use.
One common house rule I've seen to buff up ranks of pale bone is to make the mobs scale up like the similar War gift from p35 of the lexicon.
General's Escort Action
Commit Eﬀort for the day. You call up one or more Small Mobs
of divine soldiers who are suicidally loyal to you, creating one Mob
for every three levels you have, rounded up. These Mobs have the
statistics of veteran soldiers, a hit bonus equal to your character level,
magical weapons for the purposes of harming supernatural creatures,
and can perform any service human servants could. This gift can be
used only once per day, and no more than the maximum allowed
number of Mobs can exist at any one time. One Large Mob can be
called in place of two Small Mobs, and one Vast Mob in place of two
Large Mobs. The soldiers created by this gift may or may not have
individual identities depending on the preference of the Godbound,
but if slain, these individuals can still be re-summoned with the next
use of this gift.
The ability for the mobs to scale makes them much more reliable as you advance in levels.