How to beat cave 5 - Use Units- Witch, Centaur, Black Knight, Succubus, Goblin, Mermaid, Use Spells - Healing, Phoenix Bird, Hercules, Athena, and Arrows. Just keep hitting forward. When your mass army is at the front of the castle and you hear the first ring, cast Athena on your melee units and Hercules on your ranged units. Use phoenix and arrows when you have less troops and want to clear out the way. Re-post if getting to the bottom.
Sinjid is simple:
Get one block, subversion, shattered bolt or break, and get re-energize.
Don't protect your friends, they will take care of the shadows (hopefully, and if not, use the options glitch).
Simply stun sinjid, then normal attack, and right when he heals, use subversion if health is low or block. Keep on continuing until you have 30 focus left, then stun and prepare to use subversion when he charges focus.