diff --git a/src/p_acs.cpp b/src/p_acs.cpp
--- a/src/p_acs.cpp
+++ b/src/p_acs.cpp
@@ -5371,6 +5371,12 @@
 	ACSF_GetActorSectorLocation,
 	ACSF_ChangeTeamScore,
 	ACSF_SetGameplaySetting,
+	ACSF_LumpOpen,
+	ACSF_LumpReadChar,
+	ACSF_LumpReadShort,
+	ACSF_LumpReadInt,
+	ACSF_LumpReadString,
+	ACSF_LumpSize,
 
 	// ZDaemon
 	ACSF_GetTeamScore = 19620,	// (int team)
@@ -7887,6 +7893,76 @@
 			}
 			break;
 		}
+		
+		case ACSF_LumpOpen:
+		{
+			const char *name = FBehavior::StaticLookupString(args[0]);
+			
+			if( (argCount > 1) && (args[1] >= 0) )
+			{
+				int startLump = args[1] + 1;
+				return Wads.FindLump(name, &startLump);
+			}
+			
+			return Wads.CheckNumForName(name);
+		}
+		
+		case ACSF_LumpReadChar:
+		case ACSF_LumpReadShort:
+		case ACSF_LumpReadInt:
+		{
+			int size;
+			int32_t buf = 0;
+			FWadLump lump = Wads.OpenLumpNum(args[0]);
+			lump.Seek(args[1], SEEK_SET);
+			
+			switch(funcIndex)
+			{
+				case ACSF_LumpReadChar:		size = sizeof(int8_t); break;
+				case ACSF_LumpReadShort: 	size = sizeof(int16_t); break;
+				default: 					size = sizeof(int32_t); break;
+			}
+			
+			lump.Read(&buf, size);
+			
+			if( (argCount < 3) || (args[2] == 0) )
+			{
+				if(size == sizeof(int8_t))
+					return (int8_t)buf;
+				
+				if(size == sizeof(int16_t))
+					return (int16_t)buf;
+			}
+			
+			return buf;
+		}
+		
+		case ACSF_LumpReadString:
+		{
+			auto len = Wads.LumpLength(args[0]) - args[1];
+			if(len <= 0)
+				return GlobalACSStrings.AddString("");
+			
+			// [TDRR] Null terminate just in case.
+			char *buf = new char[len + 1];
+			FWadLump lump = Wads.OpenLumpNum(args[0]);
+			lump.Seek(args[1], SEEK_SET);
+			
+			lump.Read(buf, len);
+			buf[len] = '\0';
+			
+			// [TDRR] Don't trim the string to the first null terminator here,
+			// since that happens after it's converted to an FString in AddString.
+			int strIndex = GlobalACSStrings.AddString(buf);
+			delete[] buf;
+			
+			return strIndex;
+		}
+		
+		case ACSF_LumpSize:
+		{
+			return Wads.LumpLength(args[0]);
+		}
 
 		default:
 			break;