If you wanna make it like a buff when u're in killing spree and bla bla a buff will be added for xx time bla bla...
skill = SkillTable.getInstance().getInfo(721, 1);
skill.getEffects(activeChar, activeChar);
activeChar.broadcastPacket(new MagicSkillUser(activeChar, activeChar, skill.getId(), 1, skill.getHitTime(), 0));