As a GM setting a good scene can elevate an encounter from standard to something very memorable.  When dealing with an experienced group of role-players this becomes more and more difficult. Another tool that can be used to make encounters rich is misdirection. And this is wonderfully where the Ettercap falls neatly into both of these categories.
Ettercaps are typically 6 feet tall and weigh about 200 pounds of creepy arachinidlike humanoid ugly. They are solitary creatures and rarely group with others of their kind, even to mate. When they do group, they tend to attract a variety of different spiders, forming a strange collective of ettercaps and arachnids. Ettercaps are known for building cunning traps out of webs and other natural materials, using them to trap prey. They build shelters out of webbing, and use monstrous spiders as lookouts and guardians.
Whenever a giant spider encounter seems too carefully planded out,  or the PCs fall prey to a deadfall in the deep woods, it’s a safe bet an Ettercap is involved. If you have a Higher level party you can even spice up the encounter and make your Ettercap a leveled Druid with one of his Giant Spiders for an Animal Companion.. Shudder.
If you decide to have your players stumble on an Ettercap lair. Try not to give it away too soon keep  your players guessing. Soften them up with a few Giant spiders. Utilize sneak attacks and traps. Maybe your Ettercap has a potion of invisibility hes acquired from a corpse of a fallen adventure.  Attack from behind or above.  attempt to single players out by screening off one Party member from the others with spiders so the Ettercap can incapacitate the weaker members of the group.

Play to the Ettercaps strengths. Web often with his Web attacks and with the Giant spiders in his lair as well. Take advantage of  their Traps and poisons. Have no fear to prolong fights with an Ettercap. move into combat and poison a party member and then move to cover.  If played well not only can an encounter with an Ettercap be fun and exciting but a terrifying battle that your players will not forget any time soon !