Entangled is a condition that represents a creature dealing with something stuck or entwined around its limbs (if it has any) and body. An entangled creature takes a -2 penalty on attack rolls and a -4 penalty on Dexterity, can move at only half speed, and cannot charge or run. Sometimes, an entangled creature cannot move across the battlefield at all. For example, a web spell can leave you literally glued to the place where you stand. In such cases, the immobilizing effect is an extra quality of whatever attack or circumstance that caused the entanglement…
A net is equipped with a trailing rope that can limit an entangled target’s movement. The rules text doesn’t mention it, but a spider attacking with a web has the option to keep a strand connected to the target or just shoot the web as a blob. If the spider decides to keep a strand attached, the web attack works just like a net attack in which the attacker controls the trailing rope. That is, if the spider wins an opposed Strength check the target can only move within the limits that the strand allows.
A net’s trailing rope is 10 ft. long although it’s possible for the net wielder to shorten the rope’s effective length just by holding it somewhere other than the end. In the case a monstrous spider, the connecting strand is as long as the distance between the spider and target at the time the spider made the web attack.
No matter what the actual circumstances, an entangled creature can use a full-round action to escape with an Escape Artist check or tear with a Strength check. See the entangling effect’s description for the entangled creature’s options and for the check DCs. In the case of a monstrous spider, the webbing covering the entangled creature has the hp shown in the spider description. I suggest giving the trailing strand (if there is one) the same hp.
In any case, if an entangled creature attempts to cast a spell, it must make a Concentration check with a DC of 15 + the spell’s level or lose the spell. A net or a monstrous spider’s web is a bit more forgiving (at least according to the net’s weapon description). The Concentration DC is 15 and failure leaves you unable to cast the spell. I suggest, however, that you treat a net or monstrous spider’s web just like any other entangling effect, at least insofar as spell casting is concerned.
Q: If a character uses a summon monster spell and conjures a Medium fiendish monstrous spider, can the caster control the spider directly or do summoner and spider need to have a language in common? Does the spider respond to verbal commands at all?
When it appears, a summoned monster attacks the summoner’s enemies to the best of its ability. There need be no communication between summoned and summoner for that to happen. The summoned monster perceives as enemies exactly the same creatures that the spell caster perceives as enemies at the time the spell is cast, and it decides which enemy to attack based on its own assessment of the situation and the certain knowledge that is must attack. Mindless summoned creatures and those with fairly low intelligence probably just attack the nearest foe.
If the summoner wants the summoned monster to do something other than attack, to attack a specific foe, to maneuver for a better position, to change tactics, or to otherwise act as the summoner directs, there must be some mode of communication between the summoner and the summoned monster. Verbal communication generally is the most precise and reliable. Verbal communication, however, requires a common language or something that provides the equivalent, such as a tongues spell. It’s possible to direct a summoned creature’s actions through gestures, but there’s no guarantee such nonverbal commands would be understood.
Q: Let’s say that the spider from the previous example uses its web attack on a Medium target. The target has a spider climb spell active—is the target still entangled? Would there be a bonus on the saving throw?
Spider climb gives you a climb speed (with all that entails) and enables you to traverse vertical surfaces or even ceilings as well as a spider can. Spider climb does not help you deal with entangling effects, not even from spider webs.
Also, a monstrous spider’s web attack doesn’t allow a saving throw. It works like an attack with a net. The spider can shoot the net up to 50 ft. (range increment 10 ft.). The spider makes a ranged touch attack against a target up to one size category bigger than it, and on a hit, the target is entangled.